Section 1.--Costæ of nearly equal width throughout, reaching the

Transcriber's note: Text enclosed by underscores is in italics (_italics_).

Page numbers enclosed by curly braces (example: {25}) have been

incorporated to facilitate the use of the Index.

Images of the original pages are available through Internet Archive. See

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* * * * *

[Illustration: DUCK POND, CORNER OF FOURTH AND MARKET STREETS (ABOUT 1700)]

THE DIATOMACEÆ OF

PHILADELPHIA AND VICINITY

BY

CHARLES S. BOYER, A.M., F.R.M.S.

_ILLUSTRATED WITH SEVEN HUNDRED

DRAWINGS BY THE AUTHOR_

PRESS OF

J. B. LIPPINCOTT COMPANY

EAST WASHINGTON SQUARE PHILADELPHIA

1916

PREFACE

The present contribution to the local flora is intended as an introduction

to more extended research.

The study is of advantage in relation to the life history of aquatic

animals, the determination of ocean currents, as proved by polar

discoveries, the investigation of geological strata where other fossil

forms are absent, and the analysis of water supply; and, when we consider

the universal distribution of diatomaceæ in the earth, the water and even

in the air and the enormous deposits formed in past ages and still forming,

we are able to realize the importance of a knowledge of these complicated

forms and their function of purification.

The absence of descriptive works of reference in available form in this

country, the polyglot confusion of authorities abroad and the amount of

time, patience and skill required in obtaining, preparing and examining

specimens, render the study one of difficulty.

The bibliography is omitted, as it is understood by those who possess the

works of reference, and but few synonyms are given, having but little,

except historical, value, especially when it is considered that modern

investigators have no access to many of the earlier collections, when any

of these exist.

So far as the marine forms are concerned, it is probable that nearly all

occurring north of Florida are here included, and the fresh-water species

described represent a large proportion of those found east of the

Alleghanies. All of the figures are drawn to the same scale, a

magnification of eight hundred diameters, from specimens in my possession,

nearly all of which were found in or near Philadelphia.

If the work is of any value in inducing further investigation, I hope, in

the words of Julien Deby, that "those who follow my advice will find in the

study of these wonderful little organisms as much pleasure as I myself have

found."

THE AUTHOR.

{5}INTRODUCTION

The Delaware River rises in the Western Catskill Mountains, flows southward

for about three hundred and seventy-five miles, and expands into Delaware

Bay about sixty miles from the sea. Its origin is among the Devonian and

Carboniferous rocks, and in its course it passes through Silurian, Triassic

and Cretaceous formations, finally reaching the Cambrian and Laurentian

beds. It also drains regions of the glacial drift and beds which overlie

overturned Miocene strata, and are sometimes mixed with them. From the

mountains, nearly four thousand feet high, to the Bay, where the depth of

water is not greater than seventy-five feet, the diatomaceous flora, from

Alpine cascades to the salt marshes of New Jersey, contains a larger number

of species than any other equal portion of the American coast.

The city of Philadelphia, about one hundred miles from the sea, lies at the

junction of the Schuylkill with the Delaware, and much of the land near the

rivers, especially southward, is flat and low, composed of recent alluvial

deposits. In the central districts the ground is high, the deep sub-soil

being mostly a dry gravel resting upon gneiss and schist, although it is in

part composed of a bluish clay which was probably laid down in the bed of

the ancient river before the last period of the glacial drift. The blue

clay was not all deposited at the same time, as in the lower strata many

marine forms are found which do not occur in the upper layers. This is

notably the case in a deposit obtained at Spreckel's Sugar Refinery and

also at the east end of Walnut Street Bridge, where a layer of blue clay

occurs which is overlain by glacial drift. In other parts of the city

mixtures of blue clay with more recent deposits are found, including

fresh-water forms from numerous creeks and rivulets which traversed what is

now the city proper, and especially from the vicinity of Fourth and Market

Streets, where there existed as late as the year 1700 a large pond known as

the "Duck Pond" which was subject to tidal overflow from its outlet, Dock

Creek. The river water at Philadelphia is not noticeably brackish, although

the tide extends thirty miles above the city and, before the building of

Fairmount Dam, to the Falls of the Schuylkill. At certain times, when the

river is low, the influx of tide water is sufficient to produce an

abundance of brackish water diatoms at Greenwich Point. The entire absence,

however, at present, of many of the marine forms obtained in dredgings in

the Delaware opposite the city, as at Smith's Island, now removed, and in

certain well borings at Pavonia, Pensauken, Gloucester and other places in

New Jersey, where the depth reached the old blue clay, indicates conditions

quite different from those now prevalent. In the Bay itself comparatively

few living species are found, at least in any abundance.

In the study of local forms which follows, the district included may be

considered as circumscribed by the circumference of a circle having a

radius of one hundred miles from Philadelphia, containing the States of New

Jersey and Delaware, the southeastern part of {6}Pennsylvania, a portion of

Maryland on the south and extending eastward to New York Bay and Long

Island Sound as far as New Rochelle.

The greater number of fresh-water species described have been obtained from

near the city along the Darby, Crum, Ridley and Brandywine Creeks and from

various places in New Jersey, including the Pine Barren region of the

southern part of the State. Numerous collections have been made in the

Schuylkill and the various reservoirs and along the Wissahickon, "where an

Alpine gorge in miniature of singular loveliness is to be found within the

limits of a city." The fossil deposits are from well borings near Camden,

N. J., and from excavations in various parts of the city.

There appears to be no relation between the Miocene beds of the eastern

coast and the deposits here described, all of which have been formed later

than the glacial period or in an interval between two such periods.

Apparently no diatoms grew during the glacial era, at least in sufficient

abundance to leave any perceptible traces of their existence. An

examination of glacial "flour" and clays from the Catskills shows an entire

absence of these forms, and I have never found them in the milky flow from

the glaciers of the Alps nor in the constantly muddy streams in certain of

our Western States. The opacity of the water produces the same result as

the absence of light in the deep lakes of New England, where diatoms are

found only on the stalks or roots of water-plants near the shore, while in

shallow ponds, such as the small lake near the summit of Mt. Lafayette, the

growth is abundant. Certain species will grow wherever there are moisture,

light and heat, but the greater number require the presence, in small

amounts, of substances produced by the decay of animal and vegetable life.

An abundance of diatoms in fresh water is usually an indication of its

potability, while their entire absence in shallow water may be due to an

excess of bacteria.

The specimens from which the drawings are made have been collected by the

author for many years; in addition to possessing an almost complete library

on the subject, he has had the advantage of examining material obtained by

the late Mr. Lewis Woolman and numerous slides furnished by a number of

friends, including Mr. John A. Shulze, Mr. Frank J. Keeley and Mr. T.

Chalkley Palmer, to whom I here take pleasure in expressing my thanks.

The difficulties of the study are well stated by Agardh in the following

extract from the preface to his Systema Algarum:

"Because, indeed, in this respect, no one will wonder whether in the

distinction of species and reference to synonyms we have, perchance,

committed many errors. They have occurred and are bound to occur, partly

from the fact that one is not permitted to see the original specimens of

all authors; partly, because sometimes even the original specimens of these

plants are erroneous; partly, because the figures and descriptions of

authors are often lacking and imperfect....

"There is added the difficulty of the study itself of these plants, their

submerged habitat, the minuteness of their structure, the rarity of their

fruit, the change in the dried {7}plant, the impossibility of culture, the

fallacies of microscopical vision and the chaotic condition of Algology

itself to-day."

The words of Agardh, written in 1824, are almost as true to-day. The lack

of authentic specimens, which we hope will be remedied in time by the

collections of the Smithsonian Institute, numerous incorrectly labelled

slides in amateur collections, the imperfections of figures copied and

recopied, without regard to relative size or correct references, and the

confusion in the attempts to harmonize different descriptions, deter the

student at the outset. The remaining difficulties mentioned by Agardh add,

however, to the remarkable interest these forms have always had, since no

increase in optical perfection of the microscope serves to lessen the

mystery of their structure and mode of growth.

CLASSIFICATION

The few species of diatoms first discovered were included by Lyngbye,

Dillwyn, and others in the genus _Conferva_. In 1824, the species,

increased to forty-eight, were separated by Agardh into eight genera

distinguished partly by their mode of growth. But little change was made

until Heiberg, in 1863, advocated the division into symmetrical and

asymmetrical forms. Without entering upon a general review of the later

classifications, including Pfitzer's and Petit's divisions according to the

number and location of the chromatophores, or the arrangement of Prof. H.

L. Smith, because of the presence or absence of a raphe, or that of

Mereschkowsky into motile and immotile forms, the modification of all of

these methods by Schuett is here adopted, varied in accordance with certain

monographs which appear to offer advantage.

It is customary, especially among writers who are familiar with other

classes of plants, to decry any classification of diatoms according to the

markings of their siliceous envelopes. As, however, one of the chief

distinctions of the class is the possession of a more or less siliceous and

indestructible frustule, and as the cell and its contents are never seen

except within the valves, their variety forms the only available method of

identification. The cell contents, owing to the difficulty of observing

their living condition, their continued change, their lack of distinct

variation and their entire absence in fossil forms, render their

consideration as a complete method of classification an impossibility. If,

however, the cell contents can be brought into relation with the markings

of their siliceous envelope, it will be a consummation for which the future

student of these complicated forms ought to be grateful. That this result

is one to be expected may be inferred from the fact that the arrangement of

protoplasmic masses in the interior of the cell is coincident in some cases

with markings on the valve, and the character of the endochrome is assuming

a certain value in accentuating the difference between such forms as

_Pleurosigma_ and _Gyrosigma_, or in the resemblance between _Hantzschia_

and _Nitzschia_, or between _Surirella_ and _Campylodiscus_. Mereschkowsky,

however, states that it is necessary to be careful in "establishing the

relationship between diatoms based on the resemblance of their

chromatophores," {8}and further observes that in _Hantzschia amphioxys_,

_Scoliotropis latestriata_ and _Achnanthes brevipes_, three widely

separated forms, the chromatophores are essentially the same.

In one of the earliest classifications of diatoms, the individual cell

received less consideration than the nature of the filament or thallus in

which many species occur in the first stages of their growth. Those,

however, which exist in colonies at first are, sooner or later, broken up

into separate frustules, either before or at the time of their maturity or

previous to conjugation, while very many species are never seen except in a

free state. The union of frustules, therefore, is of secondary importance

and the group must be considered as filamentous or unicellular algæ. Their

relation to other algæ is not well determined. Among the _Desmidiaceæ_, a

family of the order _Conjugales_, of the class _Chlorophyceæ_, the cells

are in many forms divided by a constriction into symmetrical halves. The

Conjugales are starch forming, with walls of cellulose. In the Diatomaceæ

the starch is replaced by oil globules, while the walls of cellulose are

more or less filled with a deposit of silica. The Conjugales, however,

reproduce by zygospores and usually contain pyrenoids, as may be seen in

the parietal chromatophores of _Spirogyra_. In the class _Heterokontæ_ we

have the reserve material in the form of oil, instead of starch, but there

are no pyrenoids. To this class belongs the order _Confervaceæ_, in which

the cells are unicellular or filamentous, and to which all of the

Diatomaceæ were referred. While, therefore, Diatomaceæ have a close

affinity to the Desmidiaceæ and to the Confervaceæ, the determination of

their origin, one from another, or from a common ancestral type, appears to

be a matter of conjecture.

{9}MORPHOLOGY AND DEVELOPMENT

THE CELL

The cell membrane is composed of two usually equal parts, each of which

consists of a valve and a girdle or zone formed of cellulose modified by

silica deposited in an insoluble state from a very dilute aqueous solution.

The valves are more siliceous and robust than the girdle. Both are in most

species easily separable, or at least the bands of the girdle which may be

more or less closely fastened to the valves have a motion over each other

permitting the cell to enlarge at pleasure. The longitudinal diameter of

the cell, or the distance between the centres of the two valves, will vary

according to the convexity of the valve and the age of the frustule which

may be often determined by the width or number of the girdle bands. These,

owing to their diversity of form and arrangement, will be further described

under the generic diagnoses.

The siliceous cell-wall is covered on the outside by a layer of protoplasm

called the coleoderm. This layer may be quite thin and evident only when

treated with fuchsin or Bismarck brown, or it may be of considerable

thickness. The cell contains the cytoplasma, protoplasm, cell-sap,

endochrome, pyrenoids, oil globules and nucleus, together with certain

other less understood bodies.

The Cytoplasma is a thin skin of colorless plasma covering the entire inner

surface of the cell. It is invisible in the living cell but is evident in

plasmolysis. In long forms it is thickened at the ends and is condensed at

the plasma bridge which frequently connects the two valves and divides the

cell into two parts, each containing more or less protoplasm surrounding

the vacuole in which are found the cell-sap and certain granules. In some

forms, as Meloseira, the cytoplasma includes the entire mass of protoplasm.

The Endochrome is seen in the form of one or more bands or plates, of a

yellowish or brownish color, on the inner side of the valves or connective

zone, or in granules or irregular masses, more or less numerous, on the

inner walls, or sometimes grouped near the centre. It consists of a mixture

of chlorophyll and diatomine which differ in their relative solubility in

alcohol and in their spectroscopic analyses. The color varies from green to

a chocolate brown in proportion to the amount of diatomine. So far as the

function of the endochrome is concerned it does not appear to differ from

that of ordinary chlorophyll, absorbing, under the influence of light, the

carbon, and disengaging the oxygen of the carbonic anhydride in the water.

Diatoms do not live in absolutely pure or non-aërated water. The individual

plates or granules of the endochrome are called chromatophores. Their

number and significance will be referred to in the description of genera.

THE PYRENOIDS.--In the chromatophores of many species are found colorless,

homogeneous bodies, strongly refractive, of various shapes, usually

lenticular or fusiform, which are known as Pyrenoids (Schmitz). They are

scarcely evident in the living cell, but are distinguished by the action of

hæmatoxylin and other reagents. Flat forms occur in Surirella and

Pleurosigma, lens forms in Pinnularia, Stauroneis, Synedra, Fragilaria and

Nitzschia, while a spherical form is found in Cymbella cuspidata. The

pyrenoids are always imbedded in the chromatophore. Their growth is by

division. Schmitz considers them a part of the living chromatophore, and

their substance as working material which in excess has become resolved

into the nature of a crystal which its form sometimes resembles.

Comparisons are made between them and crystalloids found in certain

monocotyledons. The pyrenoid is evidently concerned in the formation of the

chromatophore, or in its division. Much of the conjecture, however, is due

to the behavior of pyrenoids in other plants.

{10}OIL GLOBULES.--It has been established by Pfitzer that starch and

sugar, as assimilation products, are replaced by oil in the cells of

diatoms ("da bekannlich Staerke und Zucker bei den Bacillariaceen nicht

nachzuweisen sind"). The oil drops are more or less numerous, of various

sizes, and are found in the cytoplasma, the cell-sap, and sometimes the

chromatophores. Mereschkowsky describes certain globules as elæoplasts,

which he divides into four kinds according to their number and position.

Whether all of these are oil globules is a question not yet determined.

Other bodies, known as "Buetschli granules," or volutin, and described as

"little blisters filled with a tolerably robust refractive substance," are

considered by Lauterborn to be a nitrogen reserve store. They are found in

the cytoplasma, or in the cell-sap, and can be fixed in picric acid and

stained in methylene blue.

NOTE.--For a discussion of the morphology of diatoms and a valuable résumé

of the investigations of Buetschli, Karsten, Lauterborn, Mereschkowsky,

Mueller, Pfitzer, Schuett, and others, the student is referred to "Der Bau

der Diatomzelle," by Dr. Otto Heinzerling, in "Bibliotheca Botanica," 1908.

CELL DIVISION

The growth of diatoms follows the usual method of cell division as

described by Sachs (Text Book of Botany, 2nd ed., p. 16): "The nucleus of a

cell which is about to divide becomes broader, assuming the form of a

biconcave lens, and its nucleolus breaks up into irregular granules which

together with its other granular contents begin to form a nuclear disc in

the equatorial plane. A delicate striation is now apparent in what is

becoming the long axis of the nucleus, at right angles to the nuclear disc,

and the characteristic nuclear spindle is gradually produced. The nuclear

disc splits into two halves lying side by side, each of which travels to

the corresponding pole of the nucleus; thus two nuclei are constituted

which are connected by fibrillæ."

The cell-wall and the chromatophore bands divide, each nucleus passes to

the centre, and two new cells are formed. In the meantime, to permit of

this division, the two siliceous valves separate, the girdle bands slipping

over each other, and opposite the larger or enclosing valve a new valve is

formed, the girdle band of which is seen later within the girdle of the

mother valve. Opposite the smaller valve of the original cell and adjoining

the new valve, another valve is formed which also produces a girdle within

the girdle of the smaller valve. As a result of division we have,

therefore, the valves of the original, or mother cell, the two new valves

and four girdle bands. (Pl. 40, Figs. 18 and 19.)

In the process of division, the continual formation of new valves, enclosed

in the older girdle bands, will naturally cause a reduction in the size of

the frustule. While this reduction, owing to the elasticity of the girdle,

does not always occur, I believe, yet, in most cases, the diameter is so

reduced that a rejuvenescence of growth is required. This is caused by the

production of auxospores which may appear without conjugation. In this

process, the beginning of which, in certain species, may be noticed by the

increase in the size of the girdle as in reduplication, the two valves

separate and within is formed a more or less spherical mass about twice the

size of the original frustule and which forms on its circumference two

large and often shapeless valves. These valves form others which assume the

appearance of the original valves, but larger, and proceed to grow in the

usual way. The reduction in size of the frustule seldom proceeds further

than about half the size of the type form, so that, as a general rule, it

may be stated that diatoms are not often smaller than half the larger size.

REPRODUCTION

The process of reproduction has been observed in many cases, but the

conclusions reached are somewhat at variance with each other. The auxospore

formation is simply a {11}method of rejuvenescence. When, however, the

auxospores are thrown off from filamentous diatoms, it is probable that two

may conjugate, their contents dividing each into two daughter cells which

unite into two zygospores. The usual method is the union of two frustules,

which, throwing off the old valves, coalesce into a single mass of

protoplasm which produces an auxospore, sometimes called a sporangial

frustule. It is stated that in some cases two frustules coalesce and

produce two auxospores.

The existence of spores in diatoms is a much-disputed point. While they

have never been seen, the inference that they exist is very great, as

otherwise it becomes difficult to understand the sudden growth of species

in localities and under conditions that seem to preclude the actual

presence of the living frustule. It is a matter of common observation that,

in examining collections of living forms, minute frustules or brownish

globules appear to resemble larger diatoms. In gatherings of Gomphonema,

when many specimens are sessile on the same object, numerous intermediate

sizes, varying from minute globules to the type, are seen, yet not

positively demonstrable as the same.

Conjugation, the formation of auxospores, and the actual process of cell

division are seldom seen, as they occur during the night or at least in

darkness. It is advisable in order to observe reduplication to obtain the

material about midnight and place it in very dilute alcohol. In filamentous

forms, however, the cell division is easily observed at any time in its

various stages. By immersing in picric acid (saturated solution),

transferring to very dilute alcohol which is gradually increased in

strength, and then passing through oil of cloves and finally to the

mounting medium, excellent preparations can be made. By staining with gold

chloride alone the nucleus is made apparent without further treatment.

EVOLUTION OF FORMS

It may be assumed that diatoms originated in the sea; to deny this requires

evidence of the existence of fresh-water species previous to the Miocene

period which is entirely marine. In those subject to fluctuations of the

waves, as pelagic diatoms, their existence appears to be contingent upon

the methods by which the separate frustules can cohere. Various devices,

including hooks, spiral bundles, horns and processes exuding threads of

plasma, exist for holding together the frustules. When marine forms are

found in quiet waters some of these devices, being no longer of any value,

cease to grow, although free swimming diatoms are rare. They either occur

in long chains or are stipitate or sessile. If it is further assumed that

the fresh-water diatoms are found in greater abundance in later periods,

the action of running streams makes necessary the provision of some means

by which the species may continue to colonize. This may be recognized in

the occurrence of linear forms chiefly in streams. Circular forms, such as

Cyclotella which have no raphe, are found in quiet waters, such as pools or

ditches, and never exist living in running streams. Those forms only would

be able to live in water having a more or less swift current under one of

three conditions: they must, as in Gomphonema, be adherent to surrounding

objects by a stipe; or be enclosed in a gelatinous tube, as in

Homoeocladia; or have an independent motion powerful enough to overcome the

influence of the current. It is true that many forms with a raphe have no

apparent motion. In the case of Mastogloia provision is made in a

gelatinous cushion in which the frustules are preserved. In Cocconeis, with

a true raphe in one valve only, in Epithemia, with a partial raphe, or in

certain Eunotiæ with a trace of one, we find species evidently degenerate

and parasitic. The long Synedræ, having only a median line, live in running

streams, since they are attached at one end to other algae. Forms with a

true raphe appear to be more highly developed, since they are able to seek

locations favorable to growth. Given, therefore, the structure of the

valve, the habitat may be inferred.

{12}THE MOTION OF DIATOMS

The erratic backward and forward movement of certain diatoms, especially

those of the Naviculoid group, or the slow, rolling motion of Surirella,

has been discussed in so many ways without definite conclusions that a

brief statement will be sufficient. Osmosis, the amoeboid movement of the

coleoderm, the protrusion of protoplasm or protoplasmic threads through the

raphe, the existence of actual organs of locomotion or cilia, and the lack

of synchronism in the chemical action occurring at the ends of the cell

which is sometimes divided by the plasma bridge, have been offered in

explanation. The chief objection to the theory of cyclosis appears to be

that the resultant motion is so greatly in excess of the rotation of

protoplasm in the cell. More or less motion is observed in various kinds of

free cells, but the movement of diatoms is not evident in those without

either a raphe or a keel upon which and apparently by which the phenomena

are produced.

Mr. T. Chalkley Palmer, in various articles in the Proceedings of the

Delaware County Institute of Science, especially in Vols. 1 and 3, gives

the results of exhaustive experiments. "Nothing, it would seem," he says,

"could be more conclusive as to the essential sameness of the nature of

motion in monads and diatoms, than the fact that both monads and diatoms

require oxygen in order to perform motion, that they come to rest when

oxygen becomes scarce, and that they resume their motion when oxygen is

again supplied."

He also thinks "that the living substance of the cell, more or less deeply

overlaid with coleoderm substance of varying consistency, and itself

assuming that degree of fluidity which best meets the requirements of the

situation, permeates the raphes, circulates in the keels, or in some cases

protrudes quite beyond the silica, and functions as the actual propulsive

agent."

THE FUNCTION OF DIATOMS

Of all forms of vegetation, the Diatomaceæ are, perhaps, the most

ubiquitous. Where-ever a sufficient amount of moisture, heat and light are

found, they grow. It was during the Miocene period that they first

appeared, and, as marine forms, reached their greatest development, both as

to size and beauty of marking, while their prevalence throughout the world

in enormous quantities has been often mentioned. The Miocene beds of

Richmond and Maryland continued over the Cretaceous formations of New

Jersey have outcropped in certain localities within our district, but are

not considered in this discussion.

The function of diatoms is not essentially different from that of other

algæ in providing food for aquatic animals, such as Salpæ and oysters, but

it is, however, in other respects that they are not only important but

necessary factors in the preservation of life.

"Full nature swarms with life; one wondrous mass

Of animals, or atoms organized,

Waiting the vital breath, when parent heaven

Shall bid his spirit blow. The hoary fen,

In putrid streams, emits the living cloud

Of pestilence. Thro' subterranean cells

Where searching sunbeams scarce can find a way,

Earth animated heaves."

I am not certain if Thomson fully understood the matter, but he has

remarkably described the facts. When "the vital breath" of returning spring

animates the earth, the "subterranean cells" of diatoms, the "atoms

organized," through the liberation of vast quantities of oxygen,

immediately begin the purification of the "putrid streams." Were these

streams not so purified, the accumulation of animal and vegetable débris

would eventually cause an enormous bacterial growth fatal to animal life.

{13}DIATOMACEÆ

Unicellular or filamentous. Cells either free, sessile, united in

filaments, immersed in a gelatinous envelope or in fronds composed of

branching tubes; microscopic, enclosed in a more or less siliceous envelope

(frustule), composed of two parts (valves), usually connected by an

intervening band (zone or girdle). Cell contents include yellowish or

brownish chlorophyll-like bodies which occur in one or several bands

(placcochromatic), or as variously distributed granular masses

(coccochromatic) lining the inner walls. Growth by ordinary cell division

or by auxospores; sexual multiplication by the formation of sporangia.

Valves of two kinds: (_a_) Those in which the markings or parts are more or

less concentric (Centricæ); (_b_) Those (Pennatæ) in which the parts are

more or less symmetrically divided by a line (pseudoraphe) or by a cleft

(raphe).

CENTRICÆ

Valves without a dividing line or cleft; markings more or less radiate;

transverse section of frustule circular, polygonal, or elliptical,

sometimes irregular.

Divided into four groups:

1. _Discoideæ._--Frustules (cells) discoid; valves without horns or

elevations (sometimes with processes).

2. _Solenoideæ._--Frustules with numerous girdle bands.

3. _Biddulphioideæ._--Frustules box-like, _i. e._, with the longitudinal

axis greater than in the Discoideæ. Valves with two or more angles,

elevations or horns.

4. _Rutilarioideæ._--Valves as if naviculoid, but with irregular or radial

structure.

Groups 2 and 4 are not included in our description. No. 2 contains plankton

genera only, while No. 4 consists of genera not yet found in this locality.

DISCOIDEÆ

1. _Coscinodisceæ._--Valve not divided by rays or costæ into sectors;

puncta sometimes radiate; ocelli or processes absent.

2. _Actinodisceæ._--Valve with radial striæ divided into sectors: ocelli

and processes absent.

3. _Eupodisceæ._--Valve disc-shaped with mammiform processes or one or more

ocelli.

1. COSCINODISCEÆ

(_a_) _Meloseirinæ._--Frustules short, in chains.

(_b_) _Coscinodiscinæ._--Frustules disc form, usually single, rarely in

short chains.

(_a_) MELOSEIRINÆ

1. _Meloseira._--Valve punctate, with a constriction or furrow between edge

of valve and girdle.

2. _Gaillonella._--Valve punctate, with a circular collar or crest near

edge of valve.

3. _Lysigonium._--Valve punctate, neither keeled nor constricted.

4. _Hyalodiscus._--Valve punctate in the centre; border with decussating

radial lines.

5. _Stephanopyxis._--Border of valve with a crown of thorns; valve

areolate.

6. _Pyxidicula._--Valve areolate, with a border of spines.

{14}MELOSEIRA AG. (1824), em. DE TONI (1892)

(melos, a limb or member, and seira, a chain)

Frustules globose, ellipsoidal or cylindrical, concatenate, closely joined

together. Valve either simply punctate or punctate and areolate. A

constriction of the cell-wall, forming a furrow between the edge of the

valve and the girdle, is more or less evident.

The genus Meloseira constituted by Agardh has been variously modified by

Kuetzing, Thwaites, Wm. Smith, Van Heurck, De Toni, and others. In Systema

Algarum Agardh included certain species of Conferva, of Lyngbye, Dillwyn

and others, and limited his genus to frustules more or less globose (fila

articulata ad genicula constricta), although in his Conspectus Criticus (p.

64), he modifies the description (fila teretia articulata, articulis

diametro æqualibus vel longioribus) to include M. varians. As, however,

Lysigonium Link, Gaillonella Bory, and other genera enlarged by Ehrenberg

and Kuetzing, came to be included under Meloseira, Thwaites suggested the

division of the genus into two: Orthosira, in which the frustules are not

convex at the ends and Aulacosira in which no central line is apparent but

with two distinct sulci. Wm. Smith adopts the genus Orthosira but rejects

Aulacosira, including all forms under the former genus and Meloseira,

suggesting that differences "exist in the formation of the sporangia" of

the two genera. M. varians and M. crenulata appear to form auxospores or

sporangial frustules in different ways, as will be noticed hereafter.

As, however, the present state of our knowledge is so limited and as much

confusion would result in further changing the nomenclature, I shall adopt,

for the most part, the division made by De Toni, separating Gaillonella and

Lysigonium and employing the name Meloseira as emendated in Sylloge

Algarum, although, as stated, it omits the species of Agardh. That a

further division may be necessary is indicated by the differences existing

between the Orthosira forms and the others.

ANALYSIS OF SPECIES

Frustules cylindrical and lengthened:

Valves with two distinct furrows; granules small distans

Valves with coarse granules granulata

Valves denticulate on the margin crenulata

Valves denticulate and constricted roeseana

Valves with row of large puncta on the girdle side undulata

Frustules cylindrical and compressed:

Valves punctate and areolate sulcata

The chromatophores consist of circular and compressed or irregular flat

granules which lie along the wall of the cell.

MELOSEIRA DISTANS (EHR.) KUETZ.

Frustules cylindrical, slender, with two furrows, one on each side of the

suture; valve in zone view with fine puncta in longitudinal rows; puncta in

valve view scattered. L. 7-10 µ.

_Meloseira nivalis_ Wm. Sm.

_Coscinodiscus minor_ Wm. Sm.

Fresh water. Fossil in New England deposits.

Pl. 1, Figs. 8 and 9.

NOTE.--In all species of Meloseira, as well as Gaillonella and Lysigonium,

the frustules are so closely coherent that when the filaments are broken

entire frustules are less frequently found than a union of two valves of

contiguous frustules.

{15}MELOSEIRA GRANULATA (EHR.) RALFS

Frustules cylindrical, robust, 5-18 µ in diam., with large granules in

longitudinal, sometimes spiral, lines, variable in size and arrangement in

the same filament. Valve in valve view with scattered puncta. Variable in

relative width and length, passing to M. crenulata.

_Gaillonella granulata_ Ehr.

_Orthosira punctata_ Wm. Sm.

Fresh water. Fossil at Coldspring, L. I.

Pl. 1, Fig. 10.

MELOSEIRA CRENULATA (EHR.) KUETZ.

Frustules cylindrical, with furrows on each side of the suture, 10-20 µ in

diam.; puncta in longitudinal rows. Margins of valves denticulate at the

junction of the frustules; valves with puncta scattered at the centre,

radiate at the circumference.

Common in fresh water; quite variable in size.

_Gaillonella crenulata_ Ehr.

_Orthosira orichalcea_ Wm. Sm. in part; not Conferva orichalcea. Mertens or

Gaillonella aurichalcea Ehr. and Bailey.

Pl. 1, Figs. 1 and 2.

MELOSEIRA ROESEANA RAB.

Frustules cylindrical, constricted toward each end, with coarse,

longitudinal striæ; valve convex, striæ punctate, radiating, with several

large granules at the centre. Connective zone with longitudinal rows of

fine puncta. Diam. 12-45 µ.

_Orthosira spinosa_ Grev.

Fresh water. Media, Pa. (Palmer); not common.

Pl. 1, Figs. 5 and 6.

MELOSEIRA ROESEANA VAR. EPIDENDRON (EHR.) GRUN.

Frustules denticulate at the margin; valve with coarse granules at the

centre from which radiate lines of fine puncta.

Wet rocks of the Wissahickon.

Pl. 1, Figs. 3 and 4.

MELOSEIRA UNDULATA (EHR.) KUETZ.

Frustules single or in twos, usually broader than long, constricted near

the margin. Valve with six to twelve internal projections forming with the

outline of the constriction of the valve a polygonal figure within the

circumference. Surface of the valve with radiating lines of puncta

disappearing toward the centre, at which are numerous coarse puncta.

_Meloseira gowenii_ A. Schmidt.

Blue clay of Philadelphia, especially common at Twelfth and Market Sts.

Pl. 1, Figs. 15, 16, 17.

MELOSEIRA SULCATA KUETZ.

Frustules quite robust, with diam. several times the length, deeply

furrowed at the margin, areolate and punctate. Valve with radiating striæ

disappearing toward the centre, and with a double row of cells near the

margin, the outer one having the appearance of a crown of teeth.

_Gaillonella sulcata_ Ehr.

_Paralia sulcata_ (Ehr.) Cleve.

_Paralia marina_ Heib.

{16}Marine and brackish. Common in all parts of the world, and fossil in

the Miocene. The Philadelphia form is the var. genuina Grun.

Pl. 1, Figs. 11 and 12.

In a gathering from Media of Meloseira crenulata (Palmer leg.), occasional

filaments are noticed with much longer and narrower frustules which become

enlarged in the middle and are seen to contain inner frustules in the

process of still further division, as shown in Fig. 2, Pl. 38.

Meloseira dickei Thwaites shows internal box-like cells placed one within

the other, which were supposed by Thwaites to be a method of reproduction.

Wm. Smith doubts this, but is unable to offer any explanation. In the

present form the mode of reduplication is that usually found in filamentous

forms, but in this case the presence of perfect frustules enclosing others

in the process of still further division has been heretofore unfamiliar to

me. The swelling in the middle appears to indicate that not all filamentous

diatoms are reduced in size by subdivision. In outline the valve is like

that of a "truncated cone," as described by Petit in referring to

Gaillonella granulata var. bambusina Petit (Diat. Nouv. et Rares, Jour. de

Micrographie, 1890).

GAILLONELLA BORY DE ST. VINCENT (1823)

(named after Gaillon, a botanist of Dieppe)

Frustules ellipsoidal, united in long filaments, usually found in pairs;

each valve is furnished with a circular collar or crest extending at right

angles to the convex edge. Valve hyaline at the centre from near which

radiate lines of fine puncta, 18-20 in 10 µ.

NOTE.--The original names of both Meloseira and Gaillonella are retained,

as there is no good reason for contracting the Greek diphthong in the

first, and the second is the correct spelling.

GAILLONELLA NUMMULOIDES (DILLW.) BORY

Frustules as in the generic diagnosis. Diam. 30 µ.

_Conferva nummuloides_ Dillwyn (Brit. Confervæ, p. 45, Sup. Pl. B).

_Meloseira nummuloides_ Ag.

Heiberg and O'Meara assign this species to _Lysigonium moniliforme_

(Muell.) Link, which is not keeled. While Dillwyn's and Lyngbye's figures

do not show the keel, it is probable from their descriptions that the

angular outline produced by the keel was noticed.

Marine or brackish. Coast of New Jersey; Hudson River (Bail.).

Pl. 1, Figs. 13 and 14.

_Gaillonella moniliformis_ of Bailey is this form, as he describes it as

having "two minute projections of the delicate transverse ridges seen near

the ends of the two globules belonging to a joint." (Amer. Jour. Science,

1842, p. 89, Pl. 2, Fig. 3.)

LYSIGONIUM LINK (1820)

(luo, to loose, and gonu, a joint)

Frustules globose, concatenate; valve simply punctate.

LYSIGONIUM MONILIFORME (MUELL.) LINK

Frustules usually in twos, not keeled; valve with puncta in longitudinal

lines, the puncta of the enveloping zone larger and in transverse rows. L.

25-40 µ (De Toni).

_Conferva moniliformis_ Mueller (1783).

{17}_Conferva nummuloides_ Eng. Bot. pl., 2287, not Dillwyn.

_Meloseira borreri_ Grev.

_Lysigonium nummuloides_ (Lyngb., Kuetz.) O'Meara = _Gaillonella

nummuloides_ (Dillw.) Bory. See O'Meara, p. 248.

Marine and brackish. Long Island Sound and coast of New Jersey.

Pl. 1, Fig. 7.

LYSIGONIUM VARIANS (AG.) DE TONI

Frustules cylindrical, in long filaments, slightly constricted on each side

of the suture; puncta in oblique rows in zone view. Valves 15-35 µ in diam.

(De Toni), sub-plane, with fine puncta in lines radiating from the centre.

Under medium magnification the frustules appear smooth. Very variable in

size.

_Meloseira varians_ Ag.

Fresh water. Common in ditches and springs.

Pl. 1, Figs. 18 and 19.

HYALODISCUS EHR. (1845)

(hyalos, transparent, and discus, a disc)

Frustules spheroidal; valve with a flattened, irregularly punctate

umbilicus from which proceed radiating or decussating lines of fine puncta.

ANALYSIS OF SPECIES

Valves divided into sectors stelliger

Valves not divided but interrupted by short dark lines at

intervals radiatus

Valves with very fine puncta scoticus

HYALODISCUS STELLIGER BAIL.

Valve with puncta in oblique decussating rows which, by reason of the

difference in obliquity, form numerous sectors. Umbilicus irregular, with

scattered, coarse puncta. Margin wide, striated.

_Podosira maculata_ Wm. Sm.

Blue clay. Not common.

Pl. 1, Fig. 22.

HYALODISCUS RADIATUS VAR. ARCTICA GRUN.

Valve with radiating puncta from a rather small umbilicus, the rays

interspersed with short, dark lines, having the appearance of spines, at

irregular intervals. Margin broad, striated.

_Pyxidicula radiata_ O'Meara.

The Philadelphia form corresponds exactly to Grunow's variety which has

closer puncta than the type form.

Blue clay. Rather rare.

Pl. 1, Fig. 21.

{18}HYALODISCUS SCOTICUS (KUETZ.) GRUN.

Valve small, with puncta about 24 in 10 µ, appearing hyaline.

De Toni remarks that it resembles a small form of H. subtilis which occurs

north and south of our limits and is yet likely to be recorded.

_Cyclotella scotica_ Kuetz.

_Podosira hormoides_ Wm. Sm.

Blue clay. Not rare.

Pl. 1, Fig. 20.

Endochrome in the form of four flaps or patches bound together about a

common pyrenoid. In H. subtilis numerous rod-shaped chromatophores lie in a

row and are not bound in the centre (Mereschkowsky).

STEPHANOPYXIS EHR. (1844) em. GRUN. (1884)

(stephanos, a crown, and pyxis, a kind of vase or box)

Frustules ellipsoidal, concatenate; valves tumid, of unequal convexity,

coarsely areolate, the cells in rows parallel to the longitudinal axis, not

radiate, with stray spines or teeth placed concentrically more or less near

the margin.

According to Karsten the chromatophores are round or angular discs which

lie near the connective zone.

STEPHANOPYXIS TURRIS (GREV.) RALFS

Valve cylindrical, with a crown of stout spines less than the diameter of

the valve near the margin. Cells hexagonal, about 2 in 10 µ, sometimes

punctate. The valve having the greater convexity has the larger spines,

though usually less of them.

_Creswellia turris_ Grev. (Gregory, Diat. of the Clyde, T. R. S. E., vol.

21, part 4, p. 66.)

_Stephanopyxis appendiculata_ Ehr.?

Creswellia is incorrectly based, as stated by Ralfs, on the concatenation

of the valves which was not noticed by Ehrenberg in the fossil forms. It

had been suggested by Kuetzing in Systema Algarum (p. 126).

Blue clay. Port Penn and Smith's Island.

Pl. 2, Figs. 1 and 2.

STEPHANOPYXIS CORONA (EHR.) GRUN.

Valve larger than in turris, sub-globose, coarsely areolate cells, 4-5 in

10 µ. One valve furnished with a crown of teeth shaped like the letter T

and united at the top into a ring above the margin of the valve; the other

valve with long spines more or less concentrically arranged.

Blue clay. Not common. Fossil in the Nottingham deposit.

Pl. 2, Fig. 3.

NOTE.--The diatomaceous deposit, so often called "Bermuda" or "Bermuda

tripoli," especially by foreign writers, is in reality the Miocene stratum

extending for miles along the Patuxent River near the village of

Nottingham, Md. The author is perfectly familiar with the location, having

made large collections there. The mistake in the name is due to the fact

that Prof. Bailey received material from Mr. Tuomey marked "Bermuda

Hundred," which is located near Petersburg, Va. Attempts have been made to

find material there and while there is an earth containing Miocene diatoms

at Petersburg, it does not exactly correspond to the material sent to

Ehrenberg by Bailey, who was in doubt as to the locality. The Bermuda

Islands are of coral formation and have no deposits of diatomaceous earth.

{19}PYXIDICULA EHR. (1833)

(dim. of pyxis, a box)

Frustules globular, solitary or in short fasciæ. Valve more or less

hemispherical, areolate, destitute of spines.

PYXIDICULA CRUCIATA EHR.

Valve hemispherical, with large, hexagonal cells. An inner stratum is

finely punctate.

Blue clay. Walnut St. Bridge. Rare.

Pl. 38, Fig. 8.

This form is not usually described as having punctate areolæ, but it does

not apparently differ from other forms of Pyxidicula of Ehrenberg as

described by Kuetzing (Species Algarum, pp. 21-23), including _P.

areolata_. In fact, it differs from Stephanopyxis, which is also sometimes

punctate, only in the absence of spines. In fossil deposits the absence of

an easily detached stratum is not significant. The difference, except in

size, between it and _P. mediterranea_ Grun. (V. H. S., Pl. 95, Figs. 15

and 16), I am unable to determine.

Although many species of Meloseira are fresh-water, the habitat of the

group Meloseirinæ is, in general, marine. It more nearly coincides in

structure and development with other algæ not diatomaceous, the siliceous

envelope constituting its most distinctive feature. As we proceed in the

classification, the structure both of the frustule and contents becomes

more complicated.

(_b_) COSCINODISCINÆ

1. _Cyclotella._--Valve with two concentric divisions of different

structure, one a wide border and the other a central surface.

2. _Coscinodiscus._--Valve areolate or punctate, with a narrow border of

the same structure.

CYCLOTELLA KUETZ. (1833)

(cyclos, a circle)

Frustules single or geminate, cylindrical, short, in zone view rectangular

or with undulating sides. Valve usually with smooth or punctate striæ,

centre sometimes bullose, smooth, or with granules scattered or radiating.

Chromatophores numerous along the valves (Pfitzer).

CYCLOTELLA STRIATA (KUETZ.) GRUN.

Valve 30-80 µ in diam., with coarse striæ, 7-12 in 10 µ, centre coarsely

punctate and bullose.

_Coscinodiscus striatus_ Kuetz.

_Cyclotella dallasiana_ Wm. Sm.

Common in the blue clay.

Pl. 2, Fig. 9.

CYCLOTELLA MENEGHINIANA KUETZ.

Frustule in zone view rectangular, undulated; valve, 10-20 µ in diam.,

marginal striæ robust and transversely punctate, centre radiately punctate.

_Cyclotella kuetzingiana_ Wm. Sm. (not Thwaites).

Crum Creek.

Pl. 2, Fig. 8.

{20}CYCLOTELLA MENEGHINIANA, VAR. STELLIGERA CL. AND GRUN.

Differs from the type in the coarse radiating lines at the centre.

Broomall Lake, Media.

Pl. 2, Fig. 4.

CYCLOTELLA MENEGHINIANA, VAR. STELLULIFERA CL. AND GRUN.

As in type but with the central rays granulate.

Broomall Lake, Media.

Pl. 2, Fig. 12.

CYCLOTELLA STYLORUM (BR.?) V. H.

Margin striated, the alternate striæ thickened near the border, producing

an appearance of subquadrate cells. Centre faintly granulate, the outer

border of which is encircled by 10-12 puncta, each of which is surrounded

by a small hyaline space.

Blue clay. Rare.

Van Heurck gives this form doubtfully as a variety of _striata_, while De

Toni makes it synonymous with it. Van Heurck's figure is not that of

Brightwell, but as the specimen above described is, I believe, exactly the

same as Van Heurck's, I retain his name.

Pl. 2, Fig. 10.

CYCLOTELLA COMTA (EHR.) KUETZ.

Valve with marginal striæ well marked, each third or fourth costa more

robust than the others. Central part finely striated, the striæ punctate,

radiating.

Fresh water.

Pl. 2, Fig. 7.

The form here figured is probably the variety _radiosa_ Grun. and is from a

New England specimen. It is quite likely to occur in this locality.

CYCLOTELLA OPERCULATA (AG.) KUETZ.

Frustules in zone view undulated. Angles rounded. Marginal costæ

alternating with minute spines; centre nearly smooth, depressed, convex or

flexuose.

Fresh water.

Pl. 2, Figs. 5 and 6.

The figure is drawn from a specimen from Boston, Mass., H. L. Smith Type

Slide No. 107, marked equivalent to _C. minutula_ Wm. Sm.

CYCLOTELLA ANTIQUA WM. SM.

Marginal costæ alternating with thick puncta; centre finely granulate with

subtriangular elevations. Frustules in zone view rectangular.

Blue clay.

Pl. 2, Fig. 11.

The form corresponds to the original specimens of Wm. Smith in the deposit

of Stavenger, Norway.

The genus Cyclotella comprises about seventy specific names, many of which

may be referred to other genera, while some of Ehrenberg's are incapable of

verification on account of the small size of the figures and the lack of

sufficient description. About half of the forms are marine. The fresh-water

species are usually found living in more or less stagnant water or in pools

contaminated with drainage, being an exception to the general rule that

diatoms are more abundant in water free from deleterious matter.

{21}COSCINODISCUS EHR. (1838)

(coscinon, a sieve, and discus)

Frustules solitary, cylindrical, compressed; valve circular or elliptical;

surface flat or sometimes convex near the border; markings more or less

angular, radiating, sometimes fasciculate; border usually well defined.

Central space, if present, hyaline, sometimes surrounded with a rosette of

large cells.

Chromatophores round, angular or irregular discs usually without pyrenoids

(Karsten).

Rattray's classification is here followed, so far as it refers to our

species.

_Excentrici._--Valves circular; central space absent; markings angular, in

oblique, decussating rows.

_Lineati._--Central space absent; markings angular, oblique decussating

rows straight.

_Fasciculati._--Markings fasciculate, or sometimes only near the border.

_Radiati._--Markings rounded or angular, more or less radiate.

_Elaborati._--Valves elliptical, markings rounded.

EXCENTRICI

COSCINODISCUS EXCENTRICUS EHR.

Valve with a hyaline excentric space from which proceed, usually in six

directions, rows of polygonal markings decreasing toward the narrow,

coarsely striated border, the rows appearing convex toward the centre.

Apiculi at unequal distances apart. Quite variable in size.

Common in the blue clay and along the coast.

Pl. 2, Figs. 14 and 20.

Fig. 20 is probably var. _perpusilla_ Grun. (Diat. Fr. Jos. L., Pl. 4 (D),

Fig. 7).

LINEATI

COSCINODISCUS LINEATUS EHR.

Valve circular, markings hexagonal, cells in parallel rows. Border narrow,

cellular.

Blue clay and Atlantic coast. Not common.

Pl. 3, Fig. 8.

FASCICULATI

COSCINODISCUS NITIDUS GREG.

Valve flat, markings rounded, distant, radiate, decreasing toward the

border which is coarsely striate. Quite variable in size and in the

distance between the markings.

Blue clay and Atlantic coast. Common.

Pl. 2, Fig. 18.

COSCINODISCUS NITIDULUS GRUN.

Valve usually not quite circular; markings smaller than in nitidus and

fasciculate near the border.

Blue clay.

Pl. 2, Fig. 19.

Various intermediate forms between nitidus and nitidulus occur.

COSCINODISCUS SUBTILIS EHR.

Markings polygonal, irregular at the centre, but forming numerous fasciculi

radiating {22}toward the border, the rows parallel to the central row of

each fasciculus. Border narrow with fine striæ; apiculi often present

between the fasciculi.

Blue clay and along the coast. Very common in the water supply of

Philadelphia and Camden, where the diameter seldom exceeds 40 µ and the

markings on the semi-radius are 10 in 10 µ.

Pl. 2, Fig. 17.

COSCINODISCUS DENARIUS SCHMIDT

Markings larger than in C. subtilis, equal, forming usually ten fasciculi,

each beginning near the semi-radius and containing ten parallel rows of

granules.

Common in the blue clay and sparingly along the coast.

Pl. 2, Fig. 13.

Forms are found intermediate between C. subtilis and C. denarius, as shown

in Fig. 15.

COSCINODISCUS POLYACANTHUS GRUN.

Markings angular, 10 in 10 µ, decreasing toward the border, fasciculate.

Apiculi large, twelve or more, usually inserted at the middle of each

fasciculus, and extending into the interior of the cell. The apiculi in

outline resemble the heads of horse-shoe nails, and are seen with

difficulty except when the valve is examined from the inner side. Border

narrow, striated. Diam. 70 µ.

Pensauken, N. J., artesian well.

Pl. 38, Fig. 5.

Rattray's description of _C. polyacanthus_ var. _intermedia_ Grun., from

Cape Wankarema, Siberia, gives the diam. as 60 µ, and there are about 7

markings by actual count in 10 µ in Grunow's figure (Diat. Fr. Jos. Land,

Pl. 3 (C), Fig. 25). The apiculi are more numerous, but there appears to be

little doubt of the general similarity. The Philadelphia form is abundant

in the Pensauken well deposit at a depth of 33 ft. The apiculi become quite

distinct in slides stained with silver nitrate by Mr. F. J. Keeley; they

are distinct from small apiculi sometimes evident between the fasciculi.

The specimens in the Pensauken deposit are mingled with other forms which

cannot be distinguished from _C. subtilis_. Whether the two are identical,

I am unable to determine. Rattray (Rev. Cos., p. 47) refers to H. L.

Smith's Type Slide No. 100, from rice-field mud, Savannah, Ga., as _C.

subtilis_. In Smith's slide, in my possession, a number of the forms show

faint outlines of the large apiculi and are otherwise exactly like C.

polyacanthus.

RADIATI

COSCINODISCUS VELATUS EHR.

Markings angular, decreasing slightly toward the coarsely striated border,

covered with fine puncta.

Blue clay.

Pl. 3, Fig. 2.

COSCINODISCUS MARGINATUS EHR.

Markings rounded, large, decreasing toward the broad border, which is

coarsely marked with distant striæ. The cells are punctate.

Common in the blue clay.

Pl. 3, Fig. 9.

In the fossil forms the puncta are not evident, hence the species is

usually described as not punctate.

{23}COSCINODISCUS RADIATUS EHR.

Markings polygonal, slightly decreasing toward the border where they are

much smaller; border well marked, striate. Quite variable in size.

Common in the blue clay and along the coast.

Pl. 3, Fig. 11. Fig. 1 is probably a smaller form.

COSCINODISCUS SUBAULACODISCOIDALIS RATTR.

Markings small, decreasing toward the border in somewhat fasciculate rows.

About one-third the distance from the border are five (Rattray finds six)

well-marked apiculi somewhat resembling those of Aulacodiscus. Border

narrow, hyaline.

Rare in the lower stratum of the blue clay.

Pl. 3, Fig. 4.

COSCINODISCUS ARGUS EHR.

Markings angular with central dots, increasing from the centre toward the

border, where they are smaller.

Blue clay.

Pl. 3, Fig. 7 (a small form).

COSCINODISCUS BIANGULATUS SCHMIDT

Central space and rosette absent, markings large, angular, not punctate,

with large central papillæ, decreasing toward the border. Border wide,

coarsely marked with rows of granules, and with two indentations on the

inner side distant from each other about two-thirds of the diameter.

Blue clay.

Pl. 3, Fig. 3.

Distinguished from Coscinodiscus asteromphalus var. omphalantha Grun.,

which also has two constrictions, by the absence of punctate markings.

COSCINODISCUS ASTEROMPHALUS EHR.

Central space small, surrounded by a rosette of large polygonal cells from

which radiate hexagonal cells, increasing about half way toward the border

and then slightly decreasing. Cells punctate.

Blue clay.

Pl. 2, Fig. 16; Pl. 40, Fig. 12.

COSCINODISCUS ASTEROMPHALUS VAR. OMPHALANTHA (EHR.) GRUN.

Central space absent, rosette evident. Markings 2½ in 10 µ, somewhat

smaller near the rosette and decreasing near the border, which is

constricted in two places, as in C. biangulatus.

Blue clay.

Pl. 38, Fig. 10.

COSCINODISCUS OCULUS-IRIDIS EHR.

Central space and rosette distinct; markings polygonal, not punctate, with

large papillæ, smaller near the rosette, increasing toward the semi-radius,

and then decreasing to the striated border which is comparatively narrow.

Blue clay and Atlantic coast.

Pl. 3, Fig. 10.

{24}ELABORATI

COSCINODISCUS LEWISIANUS GREV.

Valves elliptical, major axis a little more than twice the minor. From a

point, usually near one side, radiate rows of granules in lines nearly

parallel to the major axis. Border broad, with distinct striæ.

Great Sedge Island, N. J. (artesian well), and in outcrops later than the

Miocene, where it is usually found.

Pl. 3, Fig. 5.

2. ACTINODISCEÆ

ACTINOPTYCHINÆ

Valves divided into sectors alternately elevated and depressed.

(1) _Actinoptychus._--Sectors plane.

(2) _Polymyxus._--Sectors convex.

ACTINOPTYCHUS EHR. (1839) em. V. H. (1890)

(actis, a ray, and ptyx, a fold)

Frustule cylindrical, less in length than the diameter, in zone view

undulated. Valve divided into six or more sectors alternately raised and

depressed, areolate and punctate, varying in the alternate divisions. The

areolation is confined to the outer layer of the valve while the punctation

is usually on an inner valve often found detached. Processes on the border,

three or more. Umbilicus circular or angular, hyaline.

ANALYSIS OF SPECIES

Sectors, six undulatus

Sectors, eight or more, cellular heliopelta

Sectors, fourteen, punctate vulgaris

ACTINOPTYCHUS UNDULATUS (KUETZ.) RALFS

Valve areolate and punctate in quincunx, divided into six equal sectors,

alternately elevated or depressed, their areolations appearing different.

Margin well defined. Umbilicus smooth, hexagonal. Processes three,

sometimes six, inserted within the margin of each alternate division. Very

variable in size and appearance.

This is the Actinocyclus of Bailey, figured and described in Amer. Jour.

Science, 1842, p. 93, Pl. 2, Fig. 11, but not named. Kuetzing describes and

names it and refers to Bailey.

_Actinoptychus omphalopelta_ Ehr.

_Actinoptychus cellulosa_ Ehr., H. L. Smith Sp. Typ., 384.

Quite common in marine and brackish water and in the blue clay.

Pl. 4, Figs. 1, 2, 4 and 6.

ACTINOPTYCHUS VULGARIS VAR. INTERRUPTA N. VAR.

Valve with fourteen sectors, the alternate ones divided by a smooth

lanceolate space for about one-half the radius, forming with the smooth,

circular umbilicus a seven pointed star. The sectors thus divided have

coarser puncta in quincunx than the other sectors, ending in a smooth area

near the margin, and also larger black puncta scattered from the centre to

the semi-radius.

Near A. vulgaris var. neogradensis Pant.

Blue clay. Not common.

Pl. 4, Fig. 5.

{25}ACTINOPTYCHUS HELIOPELTA GRUN. VAR.?

Valve circular, sectors, eight, umbilicus circular, without rays; border

wide, cellular, with distinct rays. Inserted at a distance within the inner

edge of the border are large processes, one on each of four alternate

sectors, and two on each of the others. The sectors are cellulate and

punctate.

Near A. heliopelta var. versicolor Brun., which, however, in the specimen

in my collection from Atlantic City (artesian well), has a greater number

of processes and they are situated on the edge of the border.

Outcrop at Buckshutem, N. J. Rare.

Pl. 4, Fig. 3.

It has been quite well determined, I think, that the typical forms of A.

heliopelta occur at the base of the Miocene. At Rock Hall, Md., on the

eastern shore of Chesapeake Bay, at a depth of from 21 to 130 ft., and at

Wildwood, N. J., at a depth of from 78 to 179 ft., diatomaceous beds occur

considered by Mr. Lewis Woolman (Geol. Surv. of N. J., 1898, pp. 116-121)

"as synchronous in age," the former being deposited in the Delaware River

Delta and the latter in the Chesapeake in post-miocene times. In each of

these beds a small form of A. heliopelta is rarely found. The material at

Buckshutem is post-miocene, and the form here figured shows a marked

variation from the Miocene species and a gradual approach toward A.

undulatus.

POLYMYXUS L. W. BAIL. (1855)

Valve circular, usually divided into fourteen sectors which are on the same

plane at the centre, but the alternate ones are elevated into mammillated

projections terminated by small processes on the margin. Zone view

rectangular with undulations subconical, terminated by the processes.

POLYMYXUS CORONALIS L. W. BAIL.

Central space hyaline, rounded or slightly stellate, from which radiate

rows of fine puncta in quincunx, shown in the figure only on the alternate

elevations, the depressed interspaces being out of focus. The mammillæ are

stated by Bailey to vary from six to ten.

Very rare in the blue clay (Walnut St. Bridge). Occurs also in the Wildwood

deposit (Bull. Torrey Bot. Club, 1895, p. 261).

Pl. 4, Fig. 7, and Pl. 5, Fig. 2.

3. EUPODISCEÆ

_Aulacodiscinæ._--Valves with mammiform elevations near the border

surmounted by nipple-like processes.

AULACODISCUS--THE ONLY GENUS AS ABOVE

_Eupodiscinæ._--Valves with ocelli.

(1) _Actinocyclus._--Valve with one small ocellus; striæ radial.

(2) _Eupodiscus._--Valve with one or more ocelli; striæ not radial.

(3) _Auliscus._--Valve with large, elevated ocelli. Central area hyaline.

Markings granular and costate.

(4) _Pseudauliscus._--Valve with radiating granules. No central space.

{26}AULACODISCUS EHR. (1844) em. RATTR. (1888)

(aulax, a furrow, and discus)

Valve usually circular, plane or with an elevated zone, frequently inflated

beneath the processes; central space irregular or rounded, sometimes

absent; markings granular, radial, sometimes in a reticulum.

The genus comprises more than one hundred species most of which are fossil,

and is represented in this locality by a single form, _A. argus_, included

by Rattray in his section "Retiformes," distinguished by the presence of a

reticulum.

AULACODISCUS ARGUS (EHR.) SCHMIDT

Frustule in zone view elliptical. Valve circular, 125-190 µ in diam.,

closely covered with two kinds of markings, one, a mesh of large,

radiating, angular cells, the outer plate, and the other, radiating rows of

circular granules with hyaline spaces intervening and closer near the

border, forming the inner plate which can occasionally be seen detached.

Central space absent. The walls of the angular cells are crossed with fine

lines and are probably composed of granules compressed so closely as to

produce partial opacity, the depth of which depends in a measure not only

on the superposition of the two plates, but on the relative closeness and

thickness of the cell-walls. In a fully-developed specimen the effect is to

produce more or less triangular cells containing three or four granules. In

some cases the opacity is so great as to render detail invisible.

In the figure the valve is supposed to be divided into three sectors,

illustrating at "a" the lower plate, at "c" the combination of the upper

and lower plates, and in the other sector the cellular mesh of the upper

plate. Processes, usually three, quite robust and inserted at from

one-fourth to one-fifth the length of the radius from the border which is

striated on the inner side. A form with four processes is found in the

lower blue clay.

_Tripodiscus argus_ Ehr.

_Eupodiscus argus_ (Ehr.) Wm. Sm.

Not uncommon in the blue clay.

Pl. 4, Fig. 8.

ACTINOCYCLUS EHR. (1837)

(actis, a ray, and cyclos)

Valve circular or elliptical; surface flat at the centre, sloping toward

the border. Central space usually evident, rounded or irregular. Markings

rounded, granular, punctiform, in radial, or nearly radial, rows, sometimes

fasciculate. A nodule, more or less evident, is found near the border which

is usually striate.

Chromatophores round discs or granules.

ANALYSIS OF SPECIES

Valve circular, rows radial, hyaline lines at the border barkleyi

Valve circular, rows fasciculate moniliformis

Valve elliptical ellipticus

The nodule is generally supposed to be a thickening of the cell-wall, and,

in the opinion of Rattray, a projection outward, but "whether there may not

be at the same time a slight inward protuberance is difficult to

determine," though, as a rule, he seems to "think there is not."

{27}ACTINOCYCLUS BARKLEYI VAR. AGGREGATA RATTR.

Surface flat from centre to semi-radius. Central space irregular, sometimes

with a few scattered granules. Markings round with central dots distinct,

about 7 at the centre, decreasing in straight radial rows to 12 in 10 µ at

the border, where they form moniliform striæ. Border narrow with striæ

about 16 in 10 µ. Hyaline interspaces at the origin of the shorter rows,

but not at equal intervals. At the border, linear hyaline spaces occur at

somewhat irregular intervals between the moniliform striæ owing to the

termination of certain radial rows before they reach the circumference.

Nodule small, from one-seventh to one-fourth the radius from the border.

According to Rattray the distinction between A. ralfsii and A. barkleyi is

partly in the absence of the zone arrangement of the hyaline spaces in the

latter, and to the slight differences in the number of granules. The

variety aggregata differs from the type form of barkleyi mainly in the

distance of the nodule from the border. I have specimens from the blue clay

material at Walnut St. Bridge, and from Smith's Island, in which the

distance from the border in one case is, as stated above, quite different

from that in the other. In specimens from Morris Cove, Conn., the locality

referred to by Rattray, variations occur.

Blue clay.

Pl. 6, Fig. 1.

In the figure the subulate hyaline spaces at the border are, in some

instances, wider than usual.

ACTINOCYCLUS MONILIFORMIS RALFS

Surface flat, from centre to about five-sixths of the radius. Central space

rounded, with one or more granules. Markings, 8 in 10 µ, round, in radial

rows, fasciculate, the oblique transverse rows irregular, very slightly

decreasing until near the edge of the flattened zone, and then suddenly

decreasing and appearing as decussating lines oblique to the border.

Apiculi distinct, interfasciculate within the border. Nodule quite evident,

surrounded by a rather wide irregular hyaline space on the margin of the

flattened zone in the middle of the fasciculus. Border wide, with striæ

about 20 in 10 µ.

Blue clay. Port Penn. Not common.

Pl. 6, Fig. 2.

Equivalent to Actinocyclus ehrenbergii, H. L. S. Type Slide 10.

In a valve from Port Penn, Delaware Bay, two nodules occur nearly opposite

each other.

ACTINOCYCLUS ELLIPTICUS VAR. DELAWARENSIS N. VAR.

Valve rhombic-elliptical. Markings somewhat angular, 6 in 10 µ at the

centre where they are sub-concentric, thence decreasing in lines radiating

more or less toward the border, where they suddenly become punctiform,

striæ about 20 in 10 µ. Border equal to one-fifth the radius. A nodule is

found on the inner side of the border. Apiculi apparently absent.

The markings are larger than in the Richmond forms which are associated by

Rattray with Actinocyclus ellipticus Grun. The form corresponds closely to

Witt's Cestodiscus ovalis var.? (Witt, Polierschief. von

Archangelsk-Kurojedowo, Pl. 8, Fig. 2), except as to the border. It does

not answer to Van Heurck's figure or any other.

Blue clay. Very rare.

Pl. 3, Fig. 6.

{28}EUPODISCUS EHR. (1844)

(eu, well, pous, a foot, and discus)

Valve circular, 45-117 µ in diam. (De Toni). Central space absent, surface

plane with angular cells. At the border short, circular processes or

ocelli.

EUPODISCUS RADIATUS BAIL.

Valve with radiating hexagonal cells, sometimes slightly curved toward the

large ocelli inserted near the border which are hyaline at the centre.

Border wide, coarsely striate.

The number of ocelli heretofore recorded is four. Specimens with five

processes are found in the artesian well at St. Augustine, Fla., and in

material at Twelfth and Brandywine Sts. Mr. Hugo Bilgram has discovered

valves with three and six ocelli.

Not common in the blue clay, but abundant along the southern coast of the

Atlantic states and the Gulf of Mexico.

Not Eupodiscus radiatus Wm. Sm, which is Biddulphia smithii (Ralfs) V. H.

Pl. 5, Fig. 3.

AULISCUS EHR. (1843)

(aulax, a furrow, referring to the grooves in certain species, according to

De Toni, but preferably from auliscos, a small reed, referring to the

processes?)

Frustule cylindrical; zone with longitudinal rows of fine puncta. Valve

circular or elliptical, plane except near the processes; central area

hyaline, usually circular. Markings of two kinds, granules radiating or

scattered and radiating, costate lines, prominent or indistinct. Processes,

two or three, large, short, cylindrical, with hyaline surface, near the

ends of the major axis in a line oblique to it.

Auliscus is divided by Rattray into fourteen sections, defined chiefly by

the character and arrangement of the markings. About eighty species are

described, but as many of the forms are fossil, occuring in the Miocene of

California, Oamaru and elsewhere, and as so few species are found in this

locality, I shall refer but briefly to this division.

_Striolati._--No transverse median areas, striæ

inconspicuous punctatus

_Lineolati._--Markings distinct, pruinose, interrupted pruinosus

_Costati._--Transverse median areas usually distinct, sculptus

markings continuous, costate cælatus

AULISCUS PUNCTATUS BAIL.

Valve broadly elliptical, or suborbicular, covered with delicate

interrupted striæ radiating in sinuous lines to the circumference, more

evident on the transverse median area; puncta 3 in 10 µ, grouped into a

rounded area on each side of the median line, elsewhere scattered. Central

space rounded, processes two, large, suborbicular.

Port Penn, Delaware River. Rare.

Pl. 5, Fig. 6.

AULISCUS PRUINOSUS BAIL.

Valve elliptical, with distinct, interrupted, pruinose, irregular markings

diverging in curved lines toward the circumference in the median part and

converging toward the processes, interspersed with numerous darker markings

having the appearance of apiculi. Central space nearly circular, sometimes

with several granules. Processes large near the ends of the major axis and

not oblique to it, or scarcely so, the edges with a crenulate border.

Blue clay. Rather rare.

Pl. 5, Fig. 8.

{29}AULISCUS SCULPTUS (WM. SM.) RALFS

Valve elliptical or subcircular, median areas distinct, rounded,

circumscribed by coarse distant costæ radiating near the border where they

are more evident, and converging toward the processes. Central space

rounded, sometimes indefinite. Processes, two, circular.

Typical specimens show wide, coarse, distant costæ, but, in some cases, the

median areas are indistinctly outlined.

Blue clay.

Pl. 5, Fig. 5.

AULISCUS CÆLATUS BAIL.

Valve elliptical or subcircular, with radiating costæ, more evident around

the median areas and at the border, converging toward the processes, with

intermediate punctate radiating lines. Central space rounded or irregular.

Processes circular.

A. sculptus has coarser costæ and the interspaces are hyaline, or

apparently so, while in A. cælatus the punctate striæ between the costæ are

more evident.

Blue clay. Not uncommon.

Pl. 5, Fig. 4.

Fig. 7 is a small, indefinite form intermediate between A. sculptus and A.

cælatus. The numerous variations in this genus make it difficult to

satisfactorily differentiate the species. The size of the four above

described varies from 40 to 150 µ.

PSEUDAULISCUS A. S. (1875) AND LEUDUGER-FORTMOREL (1879)

Valve circular or subcircular, nearly flat or depressed at the centre.

Central space not evident. Processes circular, with narrow border, near the

circumference. Border narrow, striated. Markings granular, radiating,

sometimes interspersed with striæ and apiculi.

Differs from Auliscus chiefly in the absence of a central space and costæ.

PSEUDAULISCUS RADIATUS (BAIL.) RATTR.

Valve circular, or nearly so, flat. Central area with scattered granules

radiating and increasing in size outward in diverging rows toward the

border which is coarsely striated. Processes, two, circular. Two small

apiculi are inserted at about one-fifth the radius from the border near the

ends of the minor axis.

Blue clay. Rare.

Pl. 5, Fig. 9.

The apiculi are not always figured. They appear in a number of specimens

from the Miocene of Maryland, Atlantic City, Harvey Cedars and Newbern.

PSEUDAULISCUS SPINOSUS (CHRISTIAN) RATTR.

Valve subcircular or slightly quadrangular, depressed at the centre and

rising to an elevated zone near the border, the two zones separated by a

distinct line. The inner zone indistinctly reticulate with fine puncta

radiating from the centre and apiculi at intervals. The outer zone with

smaller apiculi surrounding the inner zone and with intermingled rows of

fine puncta and interrupted diverging striæ. Near each end of the minor

axis is a rather long, robust spine inserted at one-fourth the radius from

the border which is narrow and striated. Processes circular, close to the

circumference.

_Auliscus spinosus_ Christian.

Blue clay. Rare.

Pl. 5, Fig. 10.

The genus is named by Schmidt, described by Leuduger-Fortmorel and

emendated by Rattray.

{30}BIDDULPHIOIDEÆ

BIDDULPHIEÆ

(_a_) _Triceratiinæ._--Frustule cylindrical or prismatic, with three or

more sides.

(_b_) _Biddulphiinæ._--Frustule cylindroid; valve with ends elevated into

round processes or long horns.

(_c_) _Anauleæ._--Valve elliptical, lunate or triangular, with internal

septa.

(_d_) _Euodieæ._--Frustule cuneate in zone view; valve lunate.

(_a_) TRICERATIINÆ

(1) _Ditylum._--Frustule imperfectly siliceous. Zone with numerous

divisions. Valve with central spine.

(2) _Trinacria._--Processes with sharp spines.

DITYLUM BAIL. (1861)

(dis, two, and tyle, a swelling, referring to the outline of the frustule)

Frustule quadrangular, convex at the ends. Valve triangular, with

undulating sides, the angles ending in a sharp point surmounted by a

bristle. Surface of valve convex at centre from which projects a long stout

spine.

DITYLUM INTRICATUM (WEST) GRUN.

Valve with the angles separated from the central part by lines imitating

septa. Surface with radiating lines of fine puncta.

Blue clay. Rare.

Pl. 6, Fig. 4.

Detached valves only have been found in the blue clay. The form is regarded

as but slightly siliceous and, therefore, the zone or girdle not being

found in the fossil deposits, I am unable to illustrate it from material in

the vicinity. On Plate 38, Figs. 6 and 7, I have sketched the zone and

valve views of specimens found recently at Vera Cruz and labelled by H. L.

Smith Triceratum intricatum West. I can find no difference between the

recent and fossil forms of the valves. The zone is covered with fine puncta

in quincunx, not visible under ordinary illumination.

The form as figured in Plate 6 corresponds to the figure of Lithodesmium

undulatum Ehr. in Van Heurck, and West, in describing the Triceratium

undulatum Wm. Sm. (figured as T. striolatum), thought that his T.

intricatum was distinct from Ehrenberg's form on the ground that the latter

came from the "Bermuda" (Nottingham) earth and must be strongly siliceous.

Lithodesmium is characterized by the envelopment of the frustules by a

cellular membrane which does not appear, evidently, in Ditylum. D.

brightwellii is distinguished by its crown of spines on the margin;

otherwise it closely resembles D. intricatum.

TRINACRIA HEIB. (1863)

(treis, three, and acra, a point)

Valve triangular, angles elevated into spines. Cells at the margin large.

TRINACRIA PILEOLUS (EHR.) GRUN.

Valve with concave sides. Surface concave with unequal punctiform and

scattered markings with central dots. Cells at the margin large, rounded.

At the angles, which vary in elevation, a few puncta are seen.

_Triceratium pileolus_ Ehr.

Blue clay. Rare.

Pl. 6, Fig. 9.

{31}(_b_) BIDDULPHIINÆ

BIDDULPHIA GRAY (1831) em. VAN HEURCK (1885)

(a genus, constituted from Conferva biddulphiana of the English Botany,

named after a Miss Biddulph)

Frustule prismatic or subcylindrical, concatenate, filamentous, or in

zig-zag, or, as usually found, free. Zone well developed. Valve triangular,

polygonal, elliptic or subcircular, convex, more or less elevated at the

angles into processes or horns. Markings cellular or punctate.

Chromatophores, small plates of various forms.

KEY TO THE SPECIES

Valves costate biddulphiana

Valves not costate:

Markings cellular, angles elevated into horns favus

angles not elevated antediluviana

Markings punctate, angles with subconical processes and

long spines granulata

spines short rhombus

spines minute smithii

processes truncate, valve elliptical turgida

valve orbicular lævis

processes absent, valve divided by irregular lines alternans

not so divided reticulum

BIDDULPHIA BIDDULPHIANA (SMITH)

Frustule quadrangular with convex ends and rounded angles. Valve elliptical

with undulated sides, divided by septa into three or more sections.

Processes large, rounded, globular or subconical. Zone varying in width.

Surface with rounded reticulations in longitudinal and transverse rows,

except at the centre where they are concentric and smaller.

_Conferva biddulphiana_ Smith (English Botany, 1807, Pl. 1762, upper

figures).

_Diatoma biddulphianum_ Ag.

_Biddulphia pulchella_ Gray.

Blue clay. Hoboken Tunnel. Along the coast.

Pl. 7, Figs. 1, 2, 3, and 4.

Quite variable in size and number of septate divisions. Fig. 3 is an

unusual form with narrow zone, having but one row of large reticulations,

evidently a young frustule.

BIDDULPHIA FAVUS (EHR.) V. H.

Frustule quadrangular, elevated at the angles into subconical processes

oblique to the longitudinal axis. Valve triangular or quadrangular, plane,

of two layers, the outer layer composed of large hexagonal cells in rows

parallel to the sides, the inner of small puncta radiating from the centre.

Zone punctate in quincunx, never found open.

_Triceratium favus_ Ehr.

Blue clay. Common along the coast.

The quadrangular form occurs only southward.

Pl. 6, Fig. 6. At "a" a cell showing the lower punctate layer. Pl. 40, Fig.

16, a transverse section of a portion of the valve showing the cellular

structure and the punctated lower stratum.

{32}BIDDULPHIA ANTEDILUVIANA (EHR.) V. H.

Frustules quadrangular, sometimes united in zig-zag chains. Valve

quadrangular with more or less concave sides, sometimes cruciform. Surface

with angular cells arranged in concentric and radiating lines increasing

toward the circumference. At each angle is a large, rounded process, which,

as well as the secondary layer, scarcely visible, is finely punctate.

_Amphitetras antediluviana_ Ehr.

_Amphitetras tessellata_ Shad.

Blue clay. Rare.

Pl. 6, Fig. 3.

A cruciform variety occurs at Pensauken, N. J., artesian well (Coll. F. J.

Keeley).

BIDDULPHIA GRANULATA ROPER

Valve elliptical-lanceolate, convex, with diagonal rows of puncta 12 in 10

µ and sometimes with small scattered spurs. Processes inflated at the base,

obtuse at the ends, which are curved outward toward alternate sides. Near

each process and on opposite sides of the longitudinal axis is placed a

stout spine bent or curved inward near the middle. Connective zone with

diagonal rows of puncta smaller than those on the valve.

Pavonia, N. J., artesian well. Fossil in the Pleistocene. Along the coast.

Not common.

Pl. 7, Fig. 6.

BIDDULPHIA RHOMBUS (EHR.) WM. SM.

Valve rhomboidal, sometimes triangular, with subconical processes. Surface

convex with hexagonal reticulations, 7-9 in 10 µ, irregular at the centre

and radiating to the circumference. Minute spurs are scattered over the

surface, and on each side are usually two or three short spines.

Common along the coast and fossil in the Miocene and later deposits.

Pl. 7, Fig. 5 (somewhat inclined, as usually seen).

BIDDULPHIA SMITHII (RALFS) V. H.

Valve orbicular, convex, with reticulations 5 in 10 µ radiating from the

centre and decreasing toward the margin and processes which are truncate. A

short spine is found on each side half way between the processes. Zone

narrow with fine puncta 12 in 10 µ in longitudinal rows.

_Cerataulus smithii_ Ralfs.

_Eupodiscus radiatus_ Wm. Sm.

Blue clay. Along the coast southward.

Pl. 7, Fig. 8.

BIDDULPHIA TURGIDA (EHR.) WM. SM.

Valve elliptical or orbicular, surface convex. Processes very large,

cylindrical, placed obliquely and inclined by the torsion of the frustule.

Between the processes are two stout spines, one on each side, frequently

forked at the ends. Puncta fine, irregular at the centre and radiating

toward the circumference.

_Cerataulus turgidus_ Ehr.

Blue clay. Along the coast. Quite variable in size.

Pl. 7, Fig. 7.

{33}BIDDULPHIA LÆVIS EHR.

Valve suborbicular or triangular, with short, truncate processes. Surface

with fine puncta about 13 in 10 µ radiating in straight or curved lines

toward the circumference and with fine spurs at intervals. Nearer one

process than the other, and about half way between centre and

circumference, are two small spines, one on each side. Quite variable in

size.

Blue clay. Common along the coast.

Pl. 7, Fig. 9.

Fig. 10 (magnification about 260 diameters only) illustrates sporangial

frustules discovered by Mr. T. Chalkley Palmer at Reedy Island, Delaware

River. In frustules having a cylindrical form, the endochrome lines the

cell-walls in the form of granules which become congregated toward the

centre in the sporangia.

BIDDULPHIA ALTERNANS (BAIL.) V. H.

Valve triangular or, rarely, quadrangular, with sides straight or slightly

concave, usually unequal. Angles obtuse, separated from the centre by

costate lines. Surface with puncta of irregular shape, large at the centre,

with smaller puncta interspersed. In many valves several lines appearing

like costæ extend inward from the border in various directions. Angles with

small puncta in transverse and longitudinal rows.

_Triceratium alternans_ Bail.

Blue clay. Along the coast.

Pl. 6, Fig. 7 and probably Fig. 8.

BIDDULPHIA RETICULUM (EHR.)

Frustule quadrangular. Valve triangular with straight or concave sides and

rounded angles. Surface convex at the centre and angles. Markings of

unequal size, mostly larger at the centre, scattered; at the angles, small

puncta in longitudinal rows.

_Triceratium sculptum_ Shad.

_Triceratium punctatum_ Br.

_Triceratium obtusum_ Br.

For explanation of the synonymy see "Biddulphoid Forms of N. A. Diat.,"

Proc. Acad. Nat. Sci., 1900, p. 724.

Blue clay. Along the coast.

Pl. 6, Fig. 5.

(_c_) ANAULEÆ

EUNOTOGRAMMA WEISSE (1854)

(eu, well, noton, a back, and gramma)

Frustule quadrangular. Valve elliptical or lunate divided by septa which

constrict the margin. Surface flat with punctate markings.

EUNOTOGRAMMA LÆVE GRUN.

Valve lunate with obtuse ends. Septa, from four to eleven or more. Surface

with puncta in transverse and longitudinal rows, sometimes indistinct and

scattered.

Shark River. Rare. More common southward. Fossil at Buckshutem, N. J.

Pl. 7, Fig. 11, and Pl. 10, Fig. 15.

I am unable to distinguish between E. læve and E. debile, as intermediate

forms occur.

{34}TERPSINOË EHR.

(terpsinoos, gladdening?)

Frustules quadrangular, adnate in filaments, usually free. Valve elliptical

or triangular, with undulating sides divided by septa into three or more

sections.

TERPSINOË AMERICANA (BAIL.) RALFS

Valve lobed at each end or angle. Central space rounded, hyaline. Surface

with fine puncta in radiating lines.

Blue clay. Not common.

Pl. 6, Fig. 10.

TERPSINOË NOVÆ-CÆSAREÆ BOYER

Valve triangular, with concave sides and broad angles equally three-lobed,

separated from the central part by septa. Central space small or absent.

Puncta delicate, radiating or scattered. L. of side 62 µ.

Pleistocene clay at Buckshutem, N. J. Fossil at Wildwood, N. J.

T. americana, forma trigona Pant.? (Le Diatomiste, Vol. 2, p. 207.)

Pl. 6, Fig. 11.

(_d_) EUODIEÆ

EUODIA BAIL. (1860)

(derivation uncertain; apparently from euodia, fragrant, probably a

euphemism)

Frustule in zone view cuneate. Valve semi-lunate, coscinodiscoid.

EUODIA GIBBA BAIL.

Valve with rounded markings, larger and scattered at the centre, radiating

at the circumference and in indefinite straight rows at the semi-radius.

Delaware Bay (Mann).

Pl. 5, Fig. 1.

I have not seen this in the Philadelphia material. The figure is drawn from

a specimen from the Gulf Stream, S. Atlantic.

{35}PENNATÆ

Valve zygomorphous. Structure pinnate, not concentric. Valve divided either

by a true raphe or cleft or by a linear space or line imitating a raphe.

Divided into three Groups:

1. _Fragilarioideæ._--Valves without a raphe; usually with a pseudoraphe or

median line.

2. _Naviculoideæ._--Either one or both valves with a true raphe.

3. _Surirelloideæ._--Valves in which the raphe is concealed near the margin

on one or both sides of each valve in a more or less elevated keel or wing.

FRAGILARIOIDEÆ

(_a_) _Tabellarieæ._--Valve symmetrical with respect to both the

longitudinal and transverse axes; septate, not cuneate.

(_b_) _Meridioneæ._--Valve symmetrical with respect to the longitudinal

axis, asymmetrical to the transverse axis, cuneate, finely striated.

(_c_) _Fragilarieæ._--Valve of varied shape, not cuneate; costate or with

transverse rows of puncta.

(_a_) TABELLARIEÆ

Frustule in zone view rectangular, in valve view linear or

linear-elliptical, sometimes constricted in the middle, symmetrical to both

axes, not cuneate; with two or more septa or annuli.

Chromatophores numerous, granular.

_Rhabdonema._--Frustules with numerous septate partitions having one or

several foramina. Transverse costæ or rows of coarse puncta.

_Tabellaria._--Frustules with two to six nearly straight septa. Transverse

striæ subtly punctate.

_Grammatophora._--Frustules with two sinuate perforate curved septa.

Transverse striæ subtly punctate.

_Striatella._--Frustules with alternate partitions, septate or partly so.

_Attheya._--Frustules not septate but with numerous annuli.

RHABDONEMA KUETZ. (1844)

(rhabdos, a rod, and nema, a thread)

Frustules quadrangular, concatenate, composed of numerous septate

partitions with transverse costæ or rows of puncta. Valves elliptical, with

a pseudoraphe and transverse apparent costæ and punctate lines; the

partitions with one or several foramina.

Chromatophores in rosettes of various kinds (Karsten); usually parallel to

the septa.

RHABDONEMA ARCUATUM (LYNG.) KUETZ.

Valve hyaline at the ends, with transverse rows of puncta producing the

appearance of costæ between the rows; pseudoraphe distinct; foramen single.

_Diatoma arcuatum_ Lyngbye.

Common along the coast.

Pl. 8, Figs. 1, 2, and 3; Pl. 40, Fig. 10.

{36}According to T. H. Buffham (Jour. Quek. M. C., Series 2, Vol. 2, p.

131), the frustules are of two kinds, those in which the length and breadth

are the same and those which are much lengthened, with a wide hyaline

girdle frequently in the middle. At the time of fructification the smaller

frustules are attached to a larger one which produces a sporangium at the

end of the girdle from which the other end of the frustule has disappeared,

or, if the two halves of the frustule remain, two sporangia are formed.

RHABDONEMA MINUTUM KUETZ.

Frustules small; valve not smooth at the ends, elliptical or

lanceolate-elliptical, with transverse rows of puncta; pseudoraphe

distinct. Foramen single, alternating above and below in adjoining

partitions.

Common in the blue clay and along the coast.

Pl. 8, Fig. 7 and Pl. 38, Fig. 11.

RHABDONEMA ADRIATICUM KUETZ.

Valve linear-lanceolate, with smooth angles; rows of puncta transverse, the

intervals appearing as costæ, as in arcuatum. Foramina, three.

Blue clay in the Pensauken and Pavonia deposits and along the coast.

Pl. 8, Figs. 4, 5 and 6.

TABELLARIA EHR. (1839)

(tabella, a tablet)

Frustules quadrangular, adnate in filaments, frequently found in zig-zag

chains, united by a gelatinous isthmus, at length separating. Valve linear,

inflated in the middle and at the ends; striæ transverse.

Chromatophores numerous, small, along the zones.

TABELLARIA FENESTRATA (LYNG.) KUETZ.

Valve elongated; pseudoraphe narrow; transverse striæ faint. In the zone

view a straight septum is shown at each end of a valve.

Common, especially in the cedar swamps and ponds of the Pine Barren region,

N. J.

Pl. 8, Figs. 11 and 12.

TABELLARIA FLOCCULOSA (ROTH) KUETZ.

Valve linear, with median inflation larger than the terminal; pseudoraphe

rather broad in the middle; transverse striæ subtly punctate. In zone view

the frustules are quadrangular, or nearly so, with about six sometimes

curved septa at one end alternating with those on the other end.

_Conferva flocculosa_ Roth.

Common especially in the Pine Barrens of New Jersey.

Pl. 8, Figs. 8, 9 and 10.

GRAMMATOPHORA EHR. (1840)

(from gramma, a letter, and phoreo, I bear)

Frustules quadrangular, adnate, in zig-zag, united by an isthmus, or,

usually, found free; divided by two sinuate and perforate curved septa.

Valve linear or oblong, sometimes with sinuate sides, and with a

pseudoraphe and transverse punctate lines.

Chromatophores granular.

{37}GRAMMATOPHORA MARINA (LYNG.) KUETZ.

Valve linear-elliptical, with smooth apices. Septum with a wide undulation

near its origin, thence straight and incrassate at the end. Striæ in

quincunx, 18-21 in 10 µ.

_Diatoma marinum_ Lyngbye.

Blue clay. Along the coast.

Pl. 8, Figs. 17 and 18.

GRAMMATOPHORA MARINA VAR. SUBTILISSIMA (BAIL.) V. H.

Valve linear, slightly constricted near the smooth apices. Septum undulated

near its origin and then straight, incrassate at the end. Puncta in

quincunx very subtle, 34-36 in 10 µ.

_Grammatophora subtilissima_ Bail.

Grammatophora oceanica var. subtilissima (Bail.) V. H., according to De

Toni. G. marina and G. oceanica are united by some authors; the latter has

more subtle striæ.

Along the coast.

Pl. 8, Figs. 13 and 14.

GRAMMATOPHORA SERPENTINA RALFS

Valve linear-elliptical, long, measuring to 150 µ (De Toni); smooth at the

apices. Septum with numerous undulations and hooked at the apex. Puncta in

quincunx, 17 in 10 µ.

Along the coast.

Pl. 8, Fig. 21.

GRAMMATOPHORA ANGULOSA VAR. HAMULIFERA (KUETZ.) GRUN.

Frustule nearly quadrate; valve with rounded but not smooth apices. Septum

bent into a sharp angle near its origin and ending in a broad hook. Puncta

in transverse rows, 14 in 10 µ.

Along the coast.

Pl. 8, Figs. 15 and 16.

GRAMMATOPHORA ISLANDICA EHR.

Frustule oblong; valve elliptical-lanceolate. Septum robust with several

undulations and hooked at the end. Pseudoraphe distinct; transverse rows of

puncta, 10 in 10 µ.

Reported by Kuetzing in the Atlantic Ocean and by Kain at Belmar, N. J. I

have not found it on our coast and I believe, in some cases, it has been

confused with _G. angulosa_ var. _hamulifera_. The figure is drawn from an

Iceland form in H. L. Smith T. S., 186.

Pl. 8, Figs. 19 and 20.

STRIATELLA AG. (1832)

(dim. of stria, referring to the lines on the frustule)

Frustules tabulate, adnate in short, stipitate filaments, scarcely

siliceous, divided into partitions, septate or partly so at alternate ends.

{38}STRIATELLA UNIPUNCTATA (LYNG.) AG.

Frustules with numerous bent septa extending the entire length. Valve

lanceolate, somewhat unsymmetrical, subtly punctate, with pseudoraphe quite

distinct.

"The specific name is derived from the appearance of the endochrome which

in the living specimen is invariably collected in a central mass with

slender threads radiating in all directions toward the cell-wall" (Wm.

Sm.). Pyrenoids cuneate, in the centre of the endochrome, numerous.

Long Island Sound and along the coast.

Pl. 8, Figs. 22 and 23.

STRIATELLA INTERRUPTA (EHR.) HEIB.

Frustules quadrangular, with robust alternate septa extending to the

middle. Puncta in quincunx, 22 in 10 µ.

_Tessella interrupta_ Ehr.

Very rare along the coast.

Pl. 8, Fig. 24. (From a form found at Stonington, Conn.)

ATTHEYA WEST (1860)

(named after Thomas Atthey)

Frustules quadrangular, tabulate, with numerous annuli. Valve

elliptical-lanceolate, with a pseudoraphe and a central punctum. Extending

from each end is a strong spine half as long as the valve.

ATTHEYA DECORA WEST

The only species. Diagnosis of the genus. The valves are imperfectly

siliceous, scarcely visible in balsam.

Very local. Abundant at Shark River, N. J.

Pl. 8, Fig. 25.

(_b_) MERIDIONEÆ

Valve symmetrical in zone and valve view along the sagittal line, but

asymmetrical to the transverse axis, cuneate. In zone view sometimes with

wedge-shaped septa. Valve finely striated, without central and usually

without terminal nodules; a pseudoraphe present.

_Licmophora._--Frustules cuneate in stipitate fan-shaped fascicles.

_Meridion._--Frustules cuneate in spiral fascicles.

LICMOPHORA AG. (1827)

(licmos, a fan, and phoreo, I bear)

Frustules wedge-shaped, joined together into fan-shaped, stipitate

fascicles. Valve cuneate, rounded at both ends, septate. Chromatophores

granular, round or oval in our species.

{39}ANALYSIS OF SPECIES

(In accordance, so far as it relates to our species, with the

classification of C. Mereschkowsky, Diagnoses of New Licmophoræ, Nuova

Notarisia, 1901.)

Placatæ--valve narrow, striæ very fine, septa superficial flabellata

Dubiæ--valve bacilliform, septa shallow, frustule with

thick walls ovulum

Paradoxæ--valve with lower end produced, striæ fine, paradoxa

pseudoraphe distinct, septa deep gracilis

tincta

baileyi ?

Lyngbyeæ--valve narrow, attenuated at both ends, distinct,

septa deep lyngbyei

Peristriatæ--valve broad, pseudoraphe wide, striæ robust ehrenbergii

LICMOPHORA FLABELLATA (CARM.) AG.

Frustule elongate, narrow; valve narrow, lanceolate-cuneate, enlarged at

the base; striæ very fine, 30 in 10 µ.

_Echinella flabellata_ Carm.

_Licmophora splendida_ Wm. Sm.

Common along the coast.

Pl. 9, Figs. 1 and 2.

LICMOPHORA OVULUM MER.

Valve ovate, attenuated to the rounded inferior apex; pseudoraphe

indistinct, striæ fine, 24 in 10 µ. Zone view broad, cuneate, angles

rounded, inferior apex broad; frustule robust, septa superficial, straight.

(Mereschkowsky, in part.)

Atlantic City. Common.

Pl. 9, Figs. 8 and 9.

LICMOPHORA PARADOXA (LYNG.) AG.

Frustule broad, with rounded angles; septa curved; valve ovate, inferior

apex produced. Pseudoraphe distinct; striæ varying from 25 below to 30

above in 10 µ.

_Echinella paradoxa_ Lyng.

_Rhipidophora paradoxa_ Kuetz.

Along the coast.

Pl. 9, Figs. 6 and 7.

LICMOPHORA GRACILIS (EHR.) GRUN.

Frustule cuneate, narrow, with sinuate margin; valve clavate, linear at the

base; striæ, 20 to 22 in 10 µ.

New Rochelle. Along the coast.

Pl. 9, Fig. 11.

LICMOPHORA GRACILIS VAR. ELONGATA (KUETZ.) DE TONI

As in the type, but more graceful and with deeper septa.

_Rhipidophora elongata_ Kuetz.

Along the coast. Not common.

Pl. 9, Figs. 12 and 13.

{40}LICMOPHORA TINCTA (AG.) GRUN.

Frustules cuneate, narrow, usually found in twos. Valve clavate, hyaline,

rather broad at the base; septa moderately deep; pseudoraphe indistinct;

striæ, 27 at the base, 30 in the middle and 33 at the apex in 10 µ.

_Gomphonema tinctum_ Ag.

Along the coast. Abundant from about the middle of July to the middle of

August.

Pl. 9, Figs. 14 and 15.

LICMOPHORA BAILEYI (EDW.) GRUN.

Frustule broadly cuneate or with convex margins, rarely almost orbicular;

valve spatulate or ovate with slender, produced base; septa very deep;

pseudoraphe distinct; striæ 20 in 10 µ.

_Podosphenia baileyi_ (Edw.) Lewis.

Long Island Sound and upper coast of New Jersey.

This form is placed in a doubtful position by Mereschkowsky. As it

corresponds more closely to the Paradoxæ, it is placed here provisionally.

The girdle face and apex of the valve are round, the pseudoraphe is

distinct and the septa deep, but the stipe is short.

Pl. 9, Fig. 10 and Pl. 38, Figs. 3 and 4.

LICMOPHORA LYNGBYEI (KUETZ.) GRUN.

Frustule cuneate, slightly rounded at the angles. Valve oblanceolate;

pseudoraphe distinct; septa deep; striæ, 12 in 10 µ below, and 16 in 10 µ

above.

_Podosphenia lyngbyei_ Kuetz.

Along the coast.

Pl. 9, Figs. 3 and 4.

LICMOPHORA EHRENBERGII (KUETZ.) GRUN.

Frustule cuneate, broad. Valve obovate-lanceolate; pseudoraphe wide; striæ

coarse, 8 in 10 µ, moniliform.

_Podosphenia ehrenbergii_ Kuetz.

Along the coast.

Pl. 9, Fig. 5.

MERIDION AG. (1824)

(merizo, I divide)

Frustules in zone view cuneate, adnate in circular or spiral fasciæ, at

length becoming free. Valve symmetrical with respect to the longitudinal

axis, more or less cuneate; costæ and striæ transverse.

Chromatophores numerous, small, elongated, in irregular rows on the zone

(Pfitzer).

MERIDION CIRCULARE (GREV.) AG.

Transverse costæ coarse, variable in number and distance apart, sometimes

interrupted or indistinct; striæ interstitial, 16 in 10 µ.

In springs and small streams of pure water.

_Echinella circularis_ Grev.

{41}Meridion constrictum Ralfs, sometimes given as a variety of M.

circulare, differs only in the constriction below the apex. The two kinds

of frustules are usually found growing together and as the variation is

often extremely slight they are here included under the earlier name.

Pl. 10, Figs. 1, 2 and 3.

Fig. 1 represents the constricted form which is the more common. Fig. 3 is

a sporangial form.

The sporangial frustules vary in shape and size, some being long and

slender, others clavate, but they are all more or less tumid in the middle,

with costæ more indefinite than in perfect valves. All gradations occur,

one end becoming shorter until the valve has the shape of the variety known

as constrictum. It would seem, therefore, that the non-constricted form is

a passage from the sporangial to the smaller or adult form, or is of no

specific importance. All forms are found living together. The adult

frustules are the smaller ones; it is from them that the sporangia are

produced.

Meridion intermedium H. L. Smith (Amer. Quart. Mic. Jour., Vol. 1, p. 12)

is characterized by less evident costæ and is more delicate in general

appearance. Some forms are capitate and others are not. Prof. Smith

compares the M. intermedium with Peronia erinacea Bréb. and Arnott which he

has named M. erinaceum, hitherto found only in Europe, and points out the

relation of the two forms to Licmophora. An examination of the H. L. S.

type slides of the two diatoms proves that Peronia has very delicate costæ

and a distinct pseudoraphe not noticeable in Meridion. On the slide of

Peronia are frustules exactly similar to certain of the sporangial

variations of M. circulare.

The fan-like arrangement of Licmophora, the marine form, and the circular

chains of Meridion, the fresh-water genus, are similar. Both are stipitate

at the beginning of their growth.

(_c_) FRAGILARIEÆ

Divided into three sections:

_Diatominæ._--Valve circular, elliptical to linear, quadrate or cruciform,

with transverse costæ; without raphe, a pseudoraphe sometimes wanting.

_Fragilariinæ._--Valve elongate, with small central and terminal

elevations, without costæ but with transverse punctate striæ; without

genuine central nodule.

_Eunotiinæ._--Valve lunate; a raphe sometimes partially formed with

terminal nodules near the edges.

DIATOMINÆ

_Diatoma._--Frustules in filaments. Valve linear or elliptical, costate.

_Plagiogramma._--Frustules in fasciæ or free. Valve costate.

_Opephora._--Valve costate, with an inner punctate stratum.

DIATOMA DE CANDOLLE (1805) em. HEIB. (1863)

(diatemno, I cut in two)

Frustules oblong or quadrate, adnate in filaments, attached by alternate

angles and finally separating. Valve linear or elliptical, with transverse

costæ and rows of puncta and a pseudoraphe.

Chromatophores large granules without definite arrangement. (See Pl. 40,

Fig. 11.)

{42}DIATOMA VULGARE BORY.

Valve elliptical-lanceolate, with apices sometimes rostrate or capitate;

pseudoraphe narrow; costæ, 5 in 10 µ.

Common everywhere in pure fresh water and extremely variable.

Pl. 10, Figs. 9 and 10.

Var. elongatum (Ag.) = var. ehrenbergii (Kuetz.)--elliptical-lanceolate,

constricted near the apex.

Var. grande (Wm. Sm.) Grun.--linear, elongated, constricted near the

apices.

Pl. 10, Fig. 4.

Both of these varieties, with numerous intermediate forms, are abundant

near Newtown Square. Varieties of Grunow, known as breve, ovate-lanceolate;

productum, ovate-lanceolate with produced apices; capitulatum, lanceolate

with capitate extremities, are mingled together in the same gathering.

DIATOMA ANCEPS (EHR.) KIRCHN.

Valve linear with rostrate apices; costæ robust; striæ delicate, 20 in 10

µ. Zone view quadrangular.

Common in fresh water.

Pl. 10, Figs. 5 and 6. Fig. 11, Pl. 40, shows frustules containing the

nuclei and chromatophores.

DIATOMA HIEMALE (LYNG.) HEIB.

Valve ovate-lanceolate to lanceolate; apices obtuse, not produced. Costæ

not numerous, robust; striæ moniliform. Zone view quadrate, the costæ as

septa deeply dividing the valve into convex elevations.

Common in springs.

Pl. 10, Figs. 7 and 8.

In all species of Diatoma a punctum, or pore, is observed, usually at

alternate ends of the two valves, by means of which a communication exists

between adjoining frustules and causes them to adhere in zig-zag chains

when partially separated.

PLAGIOGRAMMA GREV. (1859)

(plagios, on the side, and gramma, a letter)

Frustules quadrangular, adnate in fasciæ, or free. Valve linear,

elliptical, or elliptical-lanceolate, divided by two or more median and two

terminal costæ or with a central and two terminal hyaline spaces.

Valve with two median and two terminal costæ:

Linear, pseudoraphe distinct pygmæum

Linear, with striæ at the ends wallichianum

Ovate-lanceolate obesum

Valve without costæ but with central and terminal

nodules: pseudoraphe absent tessellatum

{43}PLAGIOGRAMMA PYGMÆUM GREV.

Valve linear-elliptical; pseudoraphe distinct; rows of granules transverse,

usually six in each compartment, moniliform, three on each side.

Blue clay. Not common.

Pl. 10, Fig. 13.

PLAGIOGRAMMA WALLICHIANUM GREV.

Valve linear, rounded at the ends; pseudoraphe absent; transverse rows of

granules, six or seven in each compartment, and two or three rows of

smaller granules at each end.

Blue clay. Not common.

Pl. 10, Fig. 14.

PLAGIOGRAMMA OBESUM GREV.

Valve rhombic-lanceolate, the costæ scarcely visible; pseudoraphe rather

wide; rows of granules, about seven in each compartment, slightly

radiating.

Blue clay. Not common.

Pl. 10, Fig. 12.

PLAGIOGRAMMA TESSELLATUM GREV.

Valve elliptical-lanceolate; central space transversely elliptical to the

major axis, half the diameter of the valve; terminal spaces more or less

circular or ovate. Granular markings large, quadrangular, in transverse

rows. Pseudoraphe not distinct. As the central space does not reach the

margin, it is a question whether this form is a Plagiogramma or a new

genus.

Blue clay. Rare.

Pl. 10, Fig. 11.

OPEPHORA PETIT (1888)

(ope, an opening, and phoreo)

Frustule rectangular. Valve cuneiform, linear or elliptical-lanceolate,

with broad, transverse striæ and a well-defined pseudoraphe or median area.

The genus "portant des stries en forme de boutonnières," as Petit remarks,

is quite near Fragilaria, under which the species here described were

originally included. (See Schmidt's Atlas, Pl. 298, where numerous forms of

F. pinnata are figured.)

OPEPHORA SCHWARTZII (GRUN.) PETIT

Valve obovate-lanceolate or nearly linear with rounded apices; striæ

transverse, broad, 3 or 4 in 10 µ; median area lanceolate.

An inner stratum, with puncta in transverse rows, is apparent.

Blue clay. Not uncommon. Variable in size.

Pl. 10, Figs. 16 and 19.

OPEPHORA PACIFICA (GRUN.) PETIT

Valve linear, oblong, with rounded apices. Median area linear, narrow;

striæ punctate.

Blue clay.

Pl. 10, Fig. 18.

Petit (Diat. Cap Horn) in his diagnosis states that the valves are

cuneiform, but they are not always so.

{44}OPEPHORA PINNATA VAR. LANCEOLATA N. VAR.

Valve lanceolate; costæ slightly radiate, punctate; median area broad,

lanceolate.

Differs from O. pinnata in outline, radiation of the costæ and median area.

Blue clay. Rare.

Pl. 10, Fig. 17.

FRAGILARIINÆ

_Fragilaria._--Frustules in fasciæ. Valve with transverse striæ.

Pseudoraphe indistinct.

_Rhaphoneis._--Striæ radiate; pseudoraphe distinct.

_Dimerogramma._--Pseudoraphe broad.

_Trachysphenia._--Valve cuneiform.

_Synedra._--Valve elongate.

_Asterionella._--Frustules in star-shaped clusters.

FRAGILARIA (LYNG.) RAB.

(fragilis, because of the fasciæ easily breaking up)

Frustules rectangular, adnate in fasciæ, soon breaking up. Valve

lanceolate, oblong or elliptical in general outline, with convex or sinuate

margins; without costæ; pseudoraphe narrow or indistinct; striæ transverse.

Chromatophores vary according to species. In some they consist of four

bands on the valves; in others they are granular (Mereschkowsky).

Brun divides the genus into two sections, Fragilaria proper and Staurosira.

The former, with an indistinct pseudoraphe, includes the species virescens,

arctica, undata and linearis, while the latter, with distinct pseudoraphe,

includes capucina, harrisonii, construens and parasitica.

FRAGILARIA VIRESCENS RALFS

Frustules in long fasciæ. Valve elliptical-lanceolate, obtuse at the

apices; pseudoraphe indistinct; striæ, 17 in 10 µ, punctate.

Very common in springs and pure streams. The fasciæ are often a foot or

more in length.

Pl. 10, Figs. 20 and 21.

FRAGILARIA ARCTICA GRUN.

Valve oblong or elliptical, 10 µ in length; striæ subtle, with coarse,

short striæ at intervals on the margin and evident in zone view.

Marine. Common at Cape May, N. J.

Pl. 10, Figs. 22 and 23.

FRAGILARIA UNDATA WM. SM.

Valve in general outline linear-elliptical, with extremities produced;

striæ subtle; pseudoraphe distinct.

Fresh water.

Pl. 10, Figs. 24, 25, 27, 28 and 29.

{45}FRAGILARIA LINEARIS CSTR.

Valve linear, with rounded apices; striæ subtle; pseudoraphe indistinct.

Marine. Cape May.

Pl. 10, Fig. 37. Fig. 36 is an indeterminate form occasionally found in the

blue clay.

FRAGILARIA CAPUCINA VAR. MESOLEPTA RAB.

Valve linear, constricted at the hyaline middle; apices slightly produced;

striæ, 17 in 10 µ. Quite variable in size.

Schuylkill River. Morrisville (Keeley).

Pl. 10, Fig. 34.

FRAGILARIA HARRISONII (WM. SM.) GRUN.

Frustules rectangular, solitary or in twos. Valve cruciform; pseudoraphe

narrow, lanceolate; striæ robust, radiating in the middle, composed of

confluent puncta, larger at the circumference.

Blue clay.

Pl. 10, Fig. 31.

FRAGILARIA CONSTRUENS (EHR.) GRUN.

Valve in general outline lanceolate, with produced apices; pseudoraphe

lanceolate, distinct or broad; striæ subtle, 15 in 10 µ. L. of valve, 10-45

µ.

_Staurosira construens_ Ehr.

_Odontidium tabellaria_ Wm. Sm.

Blue clay.

Pl. 10, Fig. 30.

FRAGILARIA PARASITICA (WM. SM.)

Frustules solitary or in twos. Valve lanceolate, sometimes constricted in

the middle; pseudoraphe wide, lanceolate; striæ subtle. Parasitic on other

diatoms.

_Odontidium parasiticum_ Wm. Sm.

Not common. Media (Palmer).

In the constricted form it is known as F. construens var. binodis (Ehr.)

Grun.

Pl. 10, Fig. 35.

An examination of the synonymy of the species of Fragilaria will convince

the student of the difficulty of determining the correct name even in

well-known forms. If all of the species of Fragilaria proper have granular

chromatophores, and all of Staurosira are placcochromatic, a satisfactory

division can be made, but so long as these facts are not known in all

species, and as authors have repeatedly confused the two divisions, the

nomenclature will be uncertain. F. harrisonii is probably in any case to be

separated from the others. De Toni includes it under its original name of

Odontidium, which genus he places near to Diatoma. The number of species in

our locality is too limited to render further discussion of any value.

{46}RHAPHONEIS EHR. (1844)

(rhaphis, a needle)

Frustule in zone view linear. Valve lanceolate or elliptical-lanceolate;

pseudoraphe distinct; striæ radiating, moniliform.

RHAPHONEIS AMPHICEROS EHR.

Valve lanceolate, broad, with apices produced; striæ in curved lines,

moniliform, the large granules in longitudinal lines.

Blue clay.

Pl. 10, Fig. 38.

RHAPHONEIS AMPHICEROS VAR. RHOMBICA GRUN.

Valve as in type form but shorter, with larger and more remote granules.

Blue clay.

Pl. 10, Figs. 39 and 40.

RHAPHONEIS BELGICA VAR. INTERMEDIA GRUN.

Valve lanceolate, rostrate; granules in longitudinal and nearly transverse,

not radiating, lines.

Absecon, N. J.

Pl. 10, Fig. 41.

DIMEROGRAMMA RALFS (1861)

(dis, two, meros, a part, gramma, a letter)

Frustules quadrangular, inflated at the angles, in fasciæ. Valve ovate or

lanceolate; striæ moniliform, transverse or slightly radiate; median area

or pseudoraphe broad, lanceolate.

DIMEROGRAMMA MARINUM (GREG.) RALFS

Valve lanceolate or linear and inflated in the middle; striæ moniliform,

transverse or slightly radiate; median area linear or lanceolate, sometimes

not reaching the smooth extremities; striæ, 8 in 10 µ.

Pl. 12, Figs. 9 and 10.

Fig. 9 differs in its lanceolate outline, in having four puncta on each

side in a row, and in the striæ which are radiate.

DIMEROGRAMMA SURIRELLA (EHR.) GRUN.

Valve elliptical-lanceolate, with rounded apices; striæ moniliform,

radiate; pseudoraphe narrow, lanceolate.

Blue clay.

Pl. 12, Fig. 11.

{47}DIMEROGRAMMA MINUS (GREG.) RALFS

Valve rhombic-lanceolate; striæ punctate, radiate; pseudoraphe lanceolate;

apices smooth.

Blue clay. Along the coast.

Pl. 12, Figs. 12, 13, 14.

TRACHYSPHENIA PETIT (1877)

(trachys, rough, and sphen, a wedge)

Frustules rectangular. Valve cuneiform with coarse puncta in transverse and

longitudinal lines; pseudoraphe narrow, linear. One species only.

TRACHYSPHENIA AUSTRALIS PETIT

Characters of the genus. Valve small; puncta, 6 in 10 µ. Allied to

Dimerogramma.

Shark River, N. J. Rare.

Pl. 12, Fig. 15.

SYNEDRA EHR. (1830)

(synedrion, a sitting together)

Frustules adnate in small stipitate clusters or free. Valve elongate,

linear or linear-lanceolate; pseudoraphe distinct; costæ absent.

The genus Synedra has few distinctive characters. As Brun remarks (Diat.

des Alpes et du Jura, p. 122), the dilatation of the extremities and the

pseudo-nodule are of little value in classification, as the intermediate

forms are so numerous. Fragilaria occurs in very long ribbons or fasciæ,

Synedra in short fasciæ or radiating clusters. Fragilaria is seldom longer

than three or four times the width, while Synedra is nearly always so. The

former has fine, often subtle, markings and narrow pseudoraphe, while the

latter has coarser punctate striæ and a more distinct pseudoraphe.

Chromatophores usually consist of two bands, one on each of the valves.

Karsten states that in the marine forms the chromatophores are oval or

polygonal discs, each of which usually encloses a pyrenoid.

SYNEDRA ULNA (NITZSCH) EHR.

Frustules solitary or in twos. Valve 150-250 µ in length, linear or

linear-lanceolate, with rostrate apices; striæ, 9 in 10 µ.

Common in rivers and streams.

Pl. 11, Figs. 4, 7 and 11 (?).

Frequently interrupted in the middle. The distinction made by Wm. Smith as

to the presence or absence of the central blank space is probably not

necessary, as both forms are found which are otherwise identical.

Fig. 5 represents the formation of a sporangial frustule which differs from

the usual form in its inflated ends prolonged into rostrate apices. Figs. 1

and 6 are sporangial frustules.

{48}SYNEDRA BICEPS (KUETZ.) SCHMIDT

Valve sublanceolate, inflated at the ends, apices rounded; central space

not always distinct; pseudoraphe narrow; striæ radiate at the ends.

This is not Kuetzing's species, if the descriptions and figures are

accepted, nor is it H. L. Smith's Type No. 545, which is S. ulna var.

danica, nor is it S. biceps Wm. Smith, but it is exactly Schmidt's form

(Atlas, Pl. 303, Figs. 10-15).

Schuylkill River.

Pl. 11, Fig. 3.

SYNEDRA DANICA KUETZ.

Valve lanceolate, suddenly constricted at the rounded apices; central space

frequently absent.

Very common in streams.

Pl. 11, Fig. 2.

The figure represents an unusually large form. It differs from S. ulna only

in its apices.

SYNEDRA CAPITATA EHR.

Valve long, linear, dilated into triangular acute apices; pseudoraphe

distinct; striæ radiate at the ends.

Blue clay.

Pl. 11, Fig. 8.

SYNEDRA ACUS KUETZ.

Valve very narrow, lanceolate, acicular, with obtuse apices.

Common in the Schuylkill River.

Pl. 11, Figs. 9 and 18.

SYNEDRA GOULARDI BRÉB.

Valve constricted in the middle; apices sub-acute, sometimes slightly

rostrate or capitate; central space evident.

Neshaminy Creek (Palmer). Blue clay. Crum Creek.

Pl. 11, Figs. 12 and 13.

SYNEDRA PULCHELLA (RALFS) KUETZ.

Valve lanceolate, tapering to the sub-acute, rostrate or slightly capitate

apices; dilated at the central hyaline space; pseudoraphe distinct. Very

variable in size.

Crum Creek. Schuylkill River. Rather common.

Pl. 11, Figs. 14, 15, 16.

SYNEDRA PULCHELLA VAR. ABNORMIS MACCHIATI?

Valve as in type form, except that one end is curved like a beak, as in S.

hamata Wm. Sm., which it resembles.

Not uncommon in the Schuylkill River.

Pl. 11, Fig. 17.

SYNEDRA OXYRHYNCHUS VAR. UNDULATA GRUN.

Valve linear-lanceolate with produced rostrate apices, asymmetrical,

sigmoid; pseudoraphe narrow; pseudo-nodule large.

Common in fresh water.

Pl. 12, Fig. 1.

{49}SYNEDRA PULCHELLA VAR. FLEXELLA N. VAR.

Frustule slightly attenuated at the ends, truncate, somewhat tumid in the

middle and flexed. Valve lanceolate, with obtuse or subcapitate apices and

with two almost imperceptible constrictions at the middle producing a tumid

appearance; pseudoraphe distinct; pseudo-nodule absent. L. 56 µ; striæ,

14-16 in 10 µ.

Some valves are bent and incised on one side. The outline of the valve is

that of pulchella.

Common at Newtown Square.

Pl. 12, Fig. 2.

SYNEDRA RADIANS KUETZ.

Frustules linear, in small fasciæ. Valve 34 µ in length, linear, with

apices rostrate, obtuse, sometimes slightly capitate; pseudoraphe distinct;

striæ about 20 in 10 µ.

Fresh water.

Pl. 10, Figs. 32 and 33.

There is difficulty in recognizing S. radians K. as described and figured

by different authors. On Plate 12, Fig. 8, I have drawn a specimen from H.

L. Smith's Type Slide No. 574, labelled S. radians Kuetz., not Wm. Smith,

which, however, corresponds closely to Smith's figure (Brit. Diat. 1, Pl.

11, Fig. 89). De Toni gives S. radians Kuetz. as equivalent to S. tenera

Wm. Sm. Van Heurck's figure of S. radians, and also the figure of ulna

var., said to be synonymous with H. L. Smith's S. radians, which does not

correspond to the specimens on Smith's slide in my possession, are

confusing. In Van Heurck's Synopsis the striæ are said to be 16 or 17,

while De Toni describes them as subtle and from 17 to 24 in 10 µ. The

length is quite variable.

Several species of Synedra resemble S. radians in the mode of growth, as

they are adnate at first, in short bands, the frustules being sessile on

other plants or objects, attached at the terminal nodules which, although

scarcely visible in most forms, are probably present in all. The frustules

are not closely connected at the free end, and soon become entirely

detached.

In Diatoma and Fragilaria, we find a punctum or pore at one end of a valve,

but not in line with the pseudoraphe; in Synedra, a minute pore is usually

found in the position of the terminal nodule and, in some species,

indications of a central nodule are observed; the median line is wider but

there is no raphe. In the fresh-water Synedræ, many of which are among the

longest of diatoms, living in running streams, the terminal nodules are

much more indistinct, while the marine forms have distinct terminal

nodules, are not, as a rule, found in bands, and assume a more naviculoid

outline.

SYNEDRA VAUCHERIÆ VAR. PARVULA (KUETZ.) RAB.

Valve lanceolate, with produced or rostrate apices; pseudo-nodule wide,

excentric. L. 17 µ.

Crum Creek.

Pl. 12, Fig. 5.

Fig. 6 represents a variety with coarser striæ from the Schuylkill River.

Both are easily mistaken for Fragilaria intermedia.

{50}SYNEDRA FULGENS (GREV.) WM. SM.

Frustules geminate or flabellate on a stipe. Valve slightly inflated in the

middle and at the apices; pseudoraphe narrow; striæ finely punctate,

radiate at the ends.

Marine. Atlantic City.

Pl. 11, Fig. 10.

SYNEDRA AFFINIS KUETZ.

Valve lanceolate; striæ marginal, leaving a broad lanceolate pseudoraphe.

Common along the coast.

Pl. 12, Fig. 3.

SYNEDRA AFFINIS VAR. PARVA (KUETZ.) V. H.

Valve lanceolate, slender; striæ marginal, shorter than in the type.

_Synedra gracilis_ Kuetz.

Common along the coast.

Pl. 12, Fig. 7.

SYNEDRA AFFINIS VAR. TABULATA (AG.) V. H.

Valve linear-lanceolate; striæ, 11 in 10 µ, very short.

Not common. New Rochelle.

Pl. 12, Fig. 4.

ASTERIONELLA HASSALL (1855)

(dim. of aster, a star)

Frustules linear, slightly inflated at the ends, arranged in star-shaped

clusters which soon break up. Valve linear, unequally inflated at the ends.

ASTERIONELLA FORMOSA HASS.

Valve clavate at the ends; striæ transverse, 17 in 10 µ, pseudoraphe very

narrow or indistinct; an ovoid, hyaline area at each end.

Newark, N. J. Broomall's Lake, Media (Palmer).

Pl. 12, Figs. 19, 20, 21.

ASTERIONELLA INFLATA HEIB.

Valve linear, capitate at each end and tumid in the middle; striæ

distinctly punctate; pseudoraphe indistinct, or not apparent. L. 30 µ.

Fresh water. May's Landing, N. J.

Pl. 12, Fig. 22.

EUNOTIINÆ

_Eunotia._--Frustules either free, in fasciæ or epiphytic. Valves arcuate.

_Actinella._--Frustules, solitary or in small clusters, cuneate. Valve

inflated at one end.

{51}EUNOTIA EHR. (1837) em. GRUN. (1862)

(eu, well, and noton, a back, referring to the strong, ridged dorsum)

Frustules free, in fasciæ or epiphytic. Valve arcuate, without costæ,

transversely striated; pseudoraphe absent; pseudo-nodules at each end.

Chromatophores laminate along the concave zone and the valves.

Very many species of Eunotia have been created to differentiate size and

number of crenæ or undulations. An examination of certain fossil deposits

of New England, as well as a gathering from the blue clay of Philadelphia,

will show forms which vary infinitely. E. major and E. gracilis are

scarcely distinguishable because of the intermediate variations. The striæ

in all forms are punctate, but the puncta are frequently confluent.

ANALYSIS OF SPECIES

Eunotia is divided into two sections, Himantidium and Eunotia proper. In

Himantidium, the frustules are in fasciæ, either short or long. Among those

with short fasciæ are major, gracilis, and nymanniana; those with long

fasciæ are pectinalis, solierolii and veneris. Eunotia proper includes

frustules, free or epiphytic, in which the valves are not dentate on the

dorsal margin, such as lunaris, hemicyclus, biceps and prærupta; and those

in which the valves are dentate or crenate on the dorsum, such as monodon,

triodon, diadema and others.

The resemblance between Eunotia and Epithemia is noticeable. In both, the

epiphytic character of the valve is seen in the shape of the frustule which

is arched, and, in the free forms, is adherent at the ends only. In

Epithemia, the median is more evident than the terminal nodules. In

Eunotia, there is no median nodule, but the end nodules, in some species,

are quite evident, and a tendency is shown to produce a very short raphe.

The arrangement of puncta in valve view is similar in both genera.

SECTION 1. HIMANTIDIUM

EUNOTIA MAJOR (WM. SM.) RAB.

Valve arcuate, linear, subcapitate, recurved. Striæ punctate, 12 in 10 µ L.

90-190 µ.

Common in fresh water.

Pl. 13, Figs. 1 and 2.

EUNOTIA GRACILIS (EHR.) RAB.

Valve with sides parallel; apices slightly capitate and revolute; striæ, 10

in 10 µ. The striæ on the connective membrane more delicate than in E.

major. Intermediate forms occur.

Common in fresh water.

Pl. 13, Fig. 3. Fig. 4 is indeterminate.

EUNOTIA NYMANNIANA GRUN.

Valve small, curved, with parallel dorsal and ventral margins; apices

truncate and recurved into dorsal elevations; striæ delicate.

Blue clay. Not common.

Pl. 13, Fig. 32.

{52}EUNOTIA PECTINALIS (KUETZ.)

Valve linear, arcuate, apices slightly rostrate; striæ distinctly punctate

with puncta in longitudinal rows nearer together at the ends.

_Himantidium pectinale_ Kuetz.

Common in fresh water.

Pl. 13, Figs. 6 and 7.

The fasciæ are associated in large masses, sometimes an inch or more in

diameter, and late in August are found a foot or more in length, of a

beautiful chocolate color. Exceedingly abundant in the cedar-swamp streams

of the Pine Barren regions of New Jersey. In winter, the dead frustules

form a parchment-like coating upon the twigs, dead leaves, and other débris

on the borders of streams.

This species can scarcely be referred to Dillwyn's Conferva pectinalis, as,

in his description, quoting Mueller, he says that "the filaments are of a

dirty green color; seldom exceeding half an inch in length." Dillwyn's form

is probably Fragilaria virescens, which equals Fragilaria pectinalis Ehr.,

while Kuetzing's species is Fragilaria pectinalis Ralfs. It is not

impossible to confuse Fragilaria virescens and Eunotia pectinalis when the

zone only is seen under a low power and their mode of growth is similar.

EUNOTIA PECTINALIS VAR. UNDULATA RALFS

Valve as in type form, but with undulate margins.

Common in the cedar swamps of New Jersey.

Pl. 13, Figs. 8 and 10.

EUNOTIA PECTINALIS VAR. SOLIEROLII (KUETZ.)

Valve as in type, but with internal divisions as though in the process of

reduplication.

Not common. Moorestown, N. J. (Palmer).

Pl. 13, Fig. 9.

EUNOTIA PECTINALIS VAR. VENTRICOSA GRUN.

As in type, but with the valves tumid in the middle.

May's Landing, N. J.

Pl. 13, Fig. 12.

Fig. 11 is a form found in the blue clay. It differs in the coarser puncta

from the var. ventricosa. In outline it resembles Eunotia arcus Wm. Sm.,

which is Ceratoneis arcus (Ehr.) Kuetz., but the central nodule is not

present as in the latter form, which connects Eunotia and Cymbella. It may

be a form of E. luna Ehr. (A. S., Atlas, Pl. 286, Figs. 33 and 34.)

EUNOTIA VENERIS KUETZ.

Valve with convex dorsal and straight ventral margins, more or less

constricted near the sub-acute apices. Striæ subtle, punctate.

_Eunotia incisa_ Greg.

May's Landing, N. J. Blue clay, Pavonia, N. J.

Pl. 13, Figs. 30 and 31.

{53}EUNOTIA (PROPER)

EUNOTIA LUNARIS (EHR.) GRUN.

Frustules sessile, solitary or in clusters. Valve arcuate, narrow,

attenuated toward the apices, which are sometimes slightly rostrate or

rostrate-capitate; transverse striæ, 14 in 10 µ, punctate.

Very common in ditches, especially in the spring. Variable in length.

Pl. 12, Figs. 24 and 25.

EUNOTIA HEMICYCLUS (EHR.) RALFS

Valve semicircular, with obtuse apices; striæ transverse, punctate;

terminal nodules minute and indistinct.

Hammonton Pond, N. J. Rare.

Pl. 12, Fig. 23.

The genus Pseudo-Eunotia was created by Grunow for forms like Eunotia, but

without terminal nodules. As, however, in E. lunaris and E. hemicyclus

nodules are evident, although not so large as in many species, I include

these two forms as heretofore under Eunotia.

EUNOTIA BICEPS EHR.

Valve linear, slightly arcuate, narrow, with rounded apices somewhat

revolute; striæ, 16 in 10 µ.

May's Landing, N. J.

Pl. 13, Fig. 27.

EUNOTIA PRÆRUPTA EHR.

Valve convex on dorsal side, apices dilated and truncate; striæ distant at

centre.

Common in the blue clay.

Pl. 13, Fig. 5.

EUNOTIA PRÆRUPTA VAR. BIDENS GRUN.

Valve with two undulations; otherwise as in type.

_Eunotia bigibba_ Greg.

With the type.

Pl. 13, Fig. 19.

EUNOTIA ROBUSTA RALFS

Valve arcuate, with several or numerous dorsal ridges or crenæ which

decrease in relative size in proportion to their number. Striæ radiate,

variable in distance apart, and in size of puncta.

Ralfs included under this one name the following species named by

Ehrenberg: E. diodon (2 crenæ); E. triodon (3); E. tetraodon (4); E.

pentodon (5); E. diadema (6); E. heptodon (7); E. octodon (8); E. enneadon

(9); E. decadon (10); E. hendecadon (11); E. duodecadon (12); E. serra

(13); E. prioritis (14); all more than 20, E. polyodon. E. scalaris, with

from 15 to 17 crenæ, and E. icosodon with 20, may be added.

It is probable that all of these forms occur at May's Landing, N. J. The

forms with more than eight crenæ are comparatively rare. In the blue clay

those with from four to six are most common.

Pl. 13, Figs. 13, 14, 15, 16, 17, 21, 24, 25.

{54}EUNOTIA BACTRIANA EHR.

Valve linear, apices revolute, acute, dentate on the dorsal margin, with

one acute crena near each end.

Tom's River, N. J. Rare.

Pl. 13, Fig. 18.

EUNOTIA BIDENTULA WM. SM.

Valve with straight ventral margin, and with two undulations on the dorsum;

apices large, rounded.

May's Landing, N. J. Rare.

Pl. 13, Fig. 20 (not Schumann's form, which has angular crenæ).

EUNOTIA FORMICA EHR. VAR.?

Valve turgid in the middle and at the apices which are unilaterally

truncate.

Pensauken, N. J. (artesian well).

Pl. 13, Fig. 26 (not a typical form).

The following are forms which appear to be indeterminate, or, in any case,

are scarcely worthy of distinction by specific names, as might be said of

others of the innumerable variations of this genus:

Fig. 23, Pl. 13, probably a form of prærupta. Newtown Square.

Fig. 28, Pl. 13, from the blue clay.

Fig. 29, Pl. 13, an asymmetrical form, apparently abnormal, but not rare at

May's Landing, N. J.

Fig. 17, Pl. 38. Valve convex on the dorsal side, incised on the ventral;

striæ about 15 in 10 µ, closer at the ends; L. 30 µ. Schuylkill River.

Fig. 18, Pl. 38. Valve arcuate, asymmetrical, broader at one end; terminal

nodules large; striæ, 10 in 10 µ; L. 47 µ. Gloucester, N. J., artesian

well.

Numerous variations of the above species are illustrated in Schmidt (Atlas,

Pls. 285-291).

ACTINELLA LEWIS (1865)

(dim. of actin, a ray)

Frustules solitary, or in small clusters, sub-cuneate or nearly linear.

Valve arcuate, rounded at one end and suddenly widened at the other into a

cup-shaped or lychnoid inflation.

ACTINELLA PUNCTATA LEWIS

Valve with fine, transverse striæ; on the margin, puncta at intervals;

terminal nodules distinct.

May's Landing, N. J.

Pl. 12, Figs. 16, 17, 18.

Fig. 17, from Tom's River, N. J., is an approach toward A. brasiliensis

Grun.

Fig. 18 represents the frustules geminate, a frequent occurrence.

{55}NAVICULOIDEÆ

In discussing the Naviculoid group, the general divisions of Cleve are here

followed, and all diatoms having a true raphe are included. I have added

the genus Epithemia and also Rhopalodia, partly because they contain a

raphe of a certain kind and partly because they resemble the markings of

certain of the genus Hantzschia in the following group, although in other

respects there is probably no similarity.

The difficulty of combining the numerous genera into groups which are

naturally affiliated is avoided in the following arrangement based on

superficial similarities, and is intended merely as an artificial key. To

unite all forms having a raphe and which are symmetrical with valves

similar and not sigmoid, under the one genus Navicula, as has been the

custom previous to the publication of Cleve's monograph, would result in

associating species differing in so many respects in relation to structure

of the valve and cell contents that it seems advisable to retain the new

genera, especially as the original genus is likely to be still further

reduced when more is known of the structure and life history of the group.

KEY TO THE GENERA

Valves dissimilar. Achnantheæ

symmetrical Cocconeis

asymmetrical

to the longitudinal axis Anorthoneis

to the transverse axis Rhoicosphenia

in zone view Achnanthes

Valves similar and asymmetrical

asymmetrical to the longitudinal axis

valves parallel Cymbella

valves not parallel Amphora

valves keeled, twisted (sometimes symmetrical) Amphiprora

valves keeled Tropidoneis

valves reniform and keeled Auricula

median line sigmoid at the ends Scoliotropis

asymmetrical to the transverse axis

striæ punctate and costate Gomphoneis

striæ punctate Gomphonema

Valves similar, symmetrical and sigmoid

striæ oblique Pleurosigma

striæ at right angles Gyrosigma

Valves similar, symmetrical, not sigmoid

striæ punctate, nodules elongated Frustulia

striæ subtly punctate, central nodule forked Amphipleura

striæ punctate and reticulate, in two strata Dictyoneis

striæ punctate and alveolate, in three strata Trachyneis

striæ punctate, in two strata Brèbissonia

striæ interrupted by blank lines Anomoeoneis

striæ crossed by longitudinal lines Caloneis

striæ oblique, median fissures in opposite directions Neidium

striæ punctate and costate, median line with horns Diploneis

striæ punctate; valves separated by septate plates Mastogloia

striæ punctate, central area dilated into a stauros Stauroneis

striæ punctate, area without stauros or horns Navicula

striæ costate, not punctate Pinnularia

{56}ACHNANTHEÆ

Frustules stipitate, free or parasitic. Valves cuneate, elliptical or

suborbicular, dissimilar, bent along the transverse or the longitudinal

axes, the lower valve with a true raphe and central and terminal nodules,

the upper valve with a pseudoraphe or median line.

_Rhoicosphenia._--Stipitate; valves with transverse puncta, bent along the

transverse axis, cuneate, with diaphragms at the ends.

_Anorthoneis._--Free; puncta radiate; valves bent slightly along the

transverse axis, suborbicular.

_Cocconeis._--Parasitic; valves elliptical, usually bent along the

longitudinal axis; striæ punctate, transverse and longitudinal.

_Achnanthes._--Stipitate; valves lanceolate or elliptical, bent along the

transverse axis; striæ transverse, punctate; costæ sometimes present.

RHOICOSPHENIA GRUN. (1860)

(rhoicos, curved, and sphen, a wedge)

Frustule in zone view curved; valves cuneate, dissimilar, the upper with a

pseudoraphe, the lower with a raphe.

Chromatophore a single plate along both valves, and one of the inner walls

of the zone. Conjugation as in Gomphonema, with which it is generally

associated in classification.

RHOICOSPHENIA CURVATA (KUETZ.) GRUN.

Valve clavate, with rounded apex and base; lower valve with raphe, a narrow

axial area and slightly radiate, punctate striæ; the upper valve with a

narrow pseudoraphe and parallel striæ; a short diaphragm at the ends of

each valve. Length usually from 15 to 25 µ, but frequently of twice the

size.

Common in Crum Creek.

Pl. 19, Figs. 25, 26, 27.

ANORTHONEIS GRUN. (1868)

(anorthos, not straight)

Valves dissimilar, the upper valve with an excentric axial area, the lower

with an excentric raphe.

ANORTHONEIS EXCENTRICA (DONK.) GRUN.

Valves orbicular, with radiating, punctate striæ, closer at the

circumference, producing the appearance of a border. Axial area not

reaching the ends. Frustules occur free on the sands of the sea-shore. L.

25 to 50 µ.

Belmar, N. J.

Pl. 16, Figs. 30 and 31.

{57}COCCONEIS EHR. (1835) em. GRUN. (1868)

(coccos, a berry)

Valves elliptical, dissimilar, the upper valve with a pseudoraphe and the

lower with a genuine raphe and nodules, usually with a rim or annulus.

Frustules epiphytic.

Cocconeis is generally considered as a degenerated form of Mastogloia, as

indicated by the "obsoletely loculiferous rim." The frustules are usually

bent along the longitudinal axis, probably because of the attachment to the

curved stems of water-plants.

The cell contents of only a few species are known. In C. pediculus, a

single chromatophore occurs on the inside of the upper valve. In

conjugation, two cells open and secrete a gelatinous mass from which an

auxospore is formed.

Cleve separates the forms having a loculiferous rim (Cocconeis) from those

without a rim (Eucocconeis). As the rim is easily detachable, the

distinction is often made with difficulty.

COCCONEIS SCUTELLUM EHR.

Valves elliptical, the upper with a linear or lanceolate pseudoraphe and

coarse puncta in transverse and radiating lines; the lower valve with much

finer puncta in radiating lines, a lanceolate axial area and, sometimes, a

loculiferous rim.

Along the coast. Common, but extremely variable.

Pl. 16, Fig. 21 (upper valve). Fig. 18, var. ?

COCCONEIS SCUTELLUM VAR. ORNATA GRUN.

Upper valve with linear axial area, and transverse and radiating punctate

lines which end at the border in a double row of finer puncta; lower valve

with much finer puncta, a lanceolate axial area and a loculiferous rim.

Atlantic City. Common.

Pl. 16, Figs. 27 and 28.

The forms along the coast vary infinitely both in size and appearance. The

var. ornata is very abundant along the entire coast. In any gathering,

valves are found with or without the rim which is frequently seen detached.

The upper valve is sometimes without the double row of puncta. Fig. 21

represents an upper valve more coarsely punctate than usually occurs. Very

many intermediate forms might be noticed.

COCCONEIS PEDICULUS EHR.

Valves rhombic-elliptical, very convex, somewhat asymmetrical; the upper

valve with a linear pseudoraphe, sometimes widened near the ends, and

slightly radiating, finely punctate striæ; lower valve with narrow, axial

area and finely punctate, radiating striæ.

Not uncommon in fresh water. Abundant in a ditch at Paoli, Pa.

Pl. 16, Figs. 23 and 24.

COCCONEIS PLACENTULA EHR.

Valve elliptical; upper valve with a linear or lanceolate axial area, and

punctate striæ in transverse and radiating rows, the puncta at equal

distances; the lower valve with a lanceolate axial area, radiating rows of

puncta, and a wide border of finely punctate, radiating striæ, separated

from the central part of the valve by a narrow hyaline zone.

Common in salt, brackish and fresh water.

Pl. 16, Figs. 19 and 20.

{58}COCCONEIS PLACENTULA VAR. LINEATA (EHR.) V. H.

As in the type, except that the upper valve has the puncta arranged in

zig-zag, giving the appearance of sinuous, longitudinal lines.

Common along the coast.

Pl. 16, Fig. 29.

C. pediculus and C. placentula are the only species I have found in fresh

water. Cleve states that the former occurs also in brackish water.

The following are among the species placed by Cleve in a new genus,

Eucocconeis, distinguished by the absence of a loculiferous rim.

COCCONEIS DIRUPTA GREG.

Valves elliptical, the lower with fine puncta in slightly radiating lines,

a narrow axial area and a central area dilated into a lanceolate,

stauriform space; the terminal fissures turned in opposite directions; the

upper valve similar to the lower valve except in the absence of raphe and

nodules.

Along the coast. New Rochelle.

Pl. 16, Fig. 22 (lower valve).

COCCONEIS PELLUCIDA GRUN.

Valves elliptical, the upper with broad axial area on each side of which

are fine, longitudinal rows of short striæ; the lower valve with more

numerous longitudinal rows, a marginal line and indistinct raphe; the

terminal fissures small and turned in opposite directions.

New Rochelle.

Pl. 16, Figs. 25 and 26.

In the var. minor Grun. the median line of the lower valve is sometimes

slightly sigmoid.

ACHNANTHES BORY (1822)

(achne, froth or down, and anthos, a flower)

Frustules stipitate, solitary or in short fasciæ, flexed. Valves elliptical

or lanceolate, naviculoid, dissimilar, the lower with a raphe and median

and terminal nodules, and the upper with a pseudoraphe or median space.

The genus has no apparent affinity with any other.

ACHNANTHES LONGIPES AG.

Valves linear-elliptical, obtuse at the apex, sometimes slightly

constricted in the middle. Connective zone with transverse, subtly punctate

striæ, interrupted by longitudinal lines. Central nodule of lower valve

dilated into a stauros reaching the margin. Valves costate, the costæ

alternating with double rows of fine puncta.

Along the coast, in estuaries.

Pl. 16, Figs. 1 and 2.

A. longipes is the only species in our locality considered by Cleve as

belonging to the genus; the other forms, distinguished by the absence of

costæ, are included in the genus Achnanthidium of Kuetzing.

In A. longipes, the chromatophores consist of scattered, rounded granules,

while in Achnanthidium the chromatophore is a single plate along the upper

valve, or a double one {59}along the connective zone. It is necessary,

therefore, to distinguish between A. longipes and the following group, but,

because of the long continued union of all of the stipitate forms having

the general appearance of a true Achnanthes, I shall continue to describe

the local species under the generally accepted name.

ACHNANTHES BREVIPES AG.

Valves without costæ; striæ moniliform; upper valve with excentric

pseudoraphe or median line; otherwise as in A. longipes.

Along the coast, in estuaries.

Pl. 16, Fig. 3.

ACHNANTHES SUBSESSILIS KUETZ.

Valves linear-elliptical, rounded at the ends; upper valve with excentric

pseudoraphe; striæ moniliform, puncta smaller than in A. brevipes.

Along the coast, in estuaries.

Pl. 16, Figs. 4, 5, 6.

The three species described above are named from the length of the stipe,

but this varies considerably and is not of special significance.

ACHNANTHES INFLATA (KUETZ.) GRUN.

Valves more or less inflated in the middle, usually with the stauros of the

lower valve asymmetrical and wider than in A. subsessilis, with which it

agrees in size and markings.

Gloucester, N. J. (artesian well).

Pl. 16, Figs. 7 and 8.

ACHNANTHES COARCTATA (BRÉB.) GRUN.

Valves lanceolate, oblong, broad at the ends and constricted in the middle.

Stauros wide; pseudoraphe of the upper valve excentric; striæ slightly

radiate on the lower valve; puncta small.

Blue clay.

Pl. 16, Fig. 9.

ACHNANTHES LANCEOLATA (BRÉB.) GRUN.

Valves more or less elliptical; striæ radiating, 12 in 10 µ, punctate; on

the lower valve a horse-shoe shaped hyaline space on one side of the

centre; on the upper valve an irregular stauros, not reaching the margin.

L. 8-20 µ.

In springs. Abundant at Newtown Square.

Pl. 16, Figs. 10, 11, 12.

ACHNANTHES EXIGUA GRUN.

Valves oblong-lanceolate, with rostrate ends, sometimes slightly

constricted in the middle. Stauros rather wide; striæ punctate, radiating,

22 in 10 µ. L. 10-12 µ.

_Stauroneis exilis_ Kuetz. (not Achnanthes exilis Kuetz.)

Frequently found in aquaria where I have kept it growing continuously for

years.

Pl. 16, Figs. 14 and 15.

ACHNANTHES LINEARIS FORMA CURTA H. L. SMITH

Frustules solitary or geminate. Valves linear-elliptical, or

elliptical-lanceolate. Lower valve without distinct axial area; upper valve

with axial area widened in the middle; striæ slightly radiate (?). L. 7 µ.

One of the smallest of diatoms.

{60}This form I found in a pure gathering covering the sides of a

greenhouse tank at Elm, N. J. It was sent to Prof. H. L. Smith, who

determined it as forma curta of A. linearis.

Pl. 16, Figs. 16 and 17.

ACHNANTHES DANICA (FLOEGEL) GRUN.

Valves rhombic-lanceolate, with subacute ends. Striæ, 25 in 10 µ, radiate.

Lower valve with stauros widened toward the margin, and cleft into three

divisions.

Pavonia, N. J. (artesian well).

Pl. 16, Fig. 13.

I have seen the lower valve only. Cleve states that the upper valve is

costate with "alternating fine lineolæ twice as close as the costæ."

CYMBELLA AG. (1830)

(cymbe, a boat)

Frustules free, stipitate or enclosed in tubes. Valve boat-shaped; median

line asymmetrical, straight or curved.

Chromatophore single, covering the entire interior of the frustule, except

the ventral part of the zone and the median lines. Its longitudinal axis is

on the dorsal part of the zone. A pyrenoid lies in a fold of the

chromatophore on the dorsal part.

The genus includes the former genera of Cocconema, characterized by

stipitate forms, and Encyonema in which the frustules are frequently

enclosed in gelatinous tubes.

SECTION 1.--CYMBELLA PROPER. FRUSTULES FREE OR SOMETIMES STIPITATE

CYMBELLA HETEROPLEURA (EHR.) KUETZ.

Valve nearly symmetrical, lanceolate, with rostrate, produced apices;

median line nearly straight; axial area linear, widened in the middle;

striæ radiate, punctate.

Blue clay.

Pl. 18, Fig. 10.

CYMBELLA CUSPIDATA KUETZ.

Valve broad, elliptical, with rostrate, somewhat acute, apices and nearly

straight, ventral margin; median line straight, axial area linear, widened

in the middle; striæ radiate, punctate.

Blue clay.

Pl. 18, Fig. 17.

CYMBELLA NAVICULIFORMIS AUERSWALD

Valve linear-elliptical, with abruptly produced apices; ventral margin

straight; median line almost straight; axial area narrow, central area

large, rounded; striæ distant in the middle, closer at the ends.

Fresh water.

Pl. 18, Fig. 6.

CYMBELLA EHRENBERGII KUETZ.

Valve lanceolate, with ventral margin nearly straight and apices

sub-rostrate; median line straight, excentric; axial area narrow; central

area widened in the middle; striæ coarsely punctate.

Fresh water.

Pl. 18, Fig. 9.

{61}CYMBELLA AFFINIS KUETZ.

Valve about three times as long as broad, strongly convex on the dorsal

side and straight on the ventral; apices sub-rostrate; striæ punctate;

axial area narrow, not widened in the middle; median line curved; a small

or indistinct punctum on the ventral side of the median line (not shown in

the figure).

Common in ponds. Abundant in East Park Reservoir.

Pl. 18, Fig. 18.

CYMBELLA EXCISA (KUETZ.) DE TONI

Valve as in affinis, but with tumid and excised ventral margin; a punctum

is found on the ventral side (not shown in the figure).

According to Cleve this is a variety of C. affinis.

Common in ponds.

Pl. 18, Figs. 15, 19?

CYMBELLA PARVA (WM. SM.) CL.

Valve semi-lanceolate, with produced apices; ventral margin slightly tumid;

axial area narrow; striæ coarsely but obscurely punctate.

C. affinis and C. parva are quite variable, the latter differing by its

lanceolate form and the absence of a punctum, which, however, is sometimes

difficult to recognize. In a gathering of C. parva, it is quite possible to

find numerous abnormal forms which appear to be sporangial, so that

specific distinctions are difficult if based on occasional specimens.

Common in ponds.

Pl. 38, Fig. 14.

CYMBELLA AMPHICEPHALA NÆGELI

Valve unequally elliptical, with broad, rostrate apices; axial area narrow;

median line straight; central area small, rounded; striæ, 12 in 10 µ on the

dorsal, closer on the ventral, side and at the ends.

Kirkwood Pond, N. J.

Pl. 18, Fig. 16.

CYMBELLA SINUATA GREG.

Valve linear-elliptical, gibbous on the ventral side; axial area

indistinct; central area widened on the ventral side nearly to the margin.

Crum Creek.

Pl. 18, Fig. 13.

SECTION 2.--COCCONEMA. FRUSTULES STIPITATE

CYMBELLA ASPERA (EHR.) CL.

Valve large, cymbiform, arcuate on the dorsal, slightly gibbous on the

ventral side; axial area linear, broad, slightly widened in the middle; no

row of puncta on the ventral side. The puncta form curved longitudinal

lines and the innermost row on the ventral side appears sometimes distant

from the others, but not as in C. cistula.

_Cocconema asperum_ Ehr.

_Cymbella gastroides_ Kuetz.

{62}Not Cymbella gastroides H. L. Smith, Type No. 118, which is C. mexicana

A. S., having a punctum in the middle of the central nodule; in outline it

is like C. gastroides var. minor Kuetz.

Blue clay.

Pl. 18, Fig. 1 (an unusual form, but it resembles Grunow's. (Diat. Franz

Jos. Land, Pl. 1, Fig. 7.)

CYMBELLA CYMBIFORMIS (KUETZ.) BRÉB.

Valve cymbiform, slightly gibbous on the ventral margin; apices broad,

somewhat truncate; a punctum occurs on the ventral side of the median line;

striæ, 8 in 10 µ, closely punctate.

Kirkwood Pond, N. J.

Pl. 18, Fig. 2.

CYMBELLA CISTULA (HEMPR.) KIRCHN.

Valve cymbiform, with gibbous ventral margin and truncate apices; a

distinct row of several puncta occurs below the median line in typical

forms.

Blue clay.

Pl. 18, Fig. 3.

CYMBELLA LANCEOLATA (EHR.) KIRCHN.

Valve cymbiform, with gibbous ventral margin; apices truncate; axial area

very narrow, scarcely widened in the middle; striæ with fine close puncta.

Kirkwood Pond, N. J.

Pl. 18, Fig. 4.

CYMBELLA MEXICANA (EHR.) A. S.

Valve broad, with gibbous ventral margin and sub-rostrate, truncate apices;

median line with reflexed terminal fissures; striæ with coarse puncta; a

large punctum occurs in the centre of the central area.

Blue clay.

Pl. 18, Fig. 5.

CYMBELLA TUMIDA (BRÉB.) V. H.

Valve cymbiform, with gibbous ventral margin and abruptly rostrate ends;

median line arcuate; axial area narrow; central area large, orbicular;

below the central nodule is a punctum; striæ punctate.

Crum Creek.

Pl. 18, Fig. 7.

SECTION 3.--ENCYONEMA. FRUSTULES IN TUBES

CYMBELLA VENTRICOSA KUETZ.

Valve lunate, with straight or slightly gibbous ventral margin; axial area

indistinct; median line straight or nearly so; striæ punctate.

Very common, but extremely variable. The ventral margin is sometimes

straight and sometimes quite gibbous.

Pl. 18, Figs. 14, 22; Pl. 38, Fig. 16; Pl. 40, Fig. 8.

{63}C. ventricosa is considered by some authors to be equivalent to C.

affinis var. semicircularis Lagerst., Encyonema prostratum (Berk.) Ralfs,

E. cæspitosum Kuetz. and E. auerswaldii Rab. H. L. Smith's Type Slide of C.

ventricosa Ag. is said to equal C. affinis Kuetz., but the specimens appear

to me to be equivalent to C. ventricosa Kuetz. Cleve unites many forms,

including E. cæspitosum, under C. ventricosa.

CYMBELLA PROSTRATA (BERK.) CL.

Valve semi-elliptical, obtuse at the apices, which are sometimes prolonged

and turned downwards; median line straight, terminal nodules distant from

the ends; axial area narrow, central area rounded; striæ in radiating,

slightly curved lines, indistinctly punctate.

Common in fresh water; occasional in brackish.

Pl. 18, Fig. 21 (represents a frequent variation).

CYMBELLA PHILADELPHICA N. SP.

Valve semi-elliptical-lanceolate, with rounded apices; ventral margin

strongly gibbous; terminal nodules distant from the ends; axial area broad,

central area widened on the dorsal side; striæ radiate, not curved nor of

unequal length, indistinctly punctate, 10 in 10 µ on the dorsal, 8 in 10 µ

on the ventral side. L. 86 µ.

This form approaches Encyonema prostratum (Berk.) Ralfs, Schmidt's Atlas,

Pl. 71, Fig. 7, but differs in the striæ and the axial and central areas.

Blue clay of Philadelphia. Rare.

Pl. 18, Fig. 8.

CYMBELLA TRIANGULUM (EHR.) CL.

Valve semi-elliptical, with acute ends; median line straight; ventral side

half the width of the dorsal, with straight, slightly convex or concave

margin; striæ radiate, coarsely punctate.

_Gloeonema triangulum_ Ehr.

Baker's Run, Willistown, Pa.

Pl. 18, Fig. 24.

CYMBELLA TURGIDA (GREG.) CL.

Valve semi-elliptical, with acute ends; ventral margin gibbous; ventral

side half the width of the dorsal; median line straight; terminal fissures

turned downwards; axial area broad; striæ radiate, coarsely punctate.

Baker's Run, Willistown, Pa.

Pl. 18, Fig. 23.

CYMBELLA TURGIDA (GREG.) CL. VAR. ?

Valve lunate, with gibbous ventral margin; median line straight; terminal

fissures turned downwards near the ends; axial area lanceolate, striæ

radiate on the dorsal side, 8 in 10 µ, punctate, 9 on the ventral side,

closer at the ends where they are convergent. L. 65 µ. Not a typical form.

Willistown, Pa.

Pl. 18, Fig. 12.

CYMBELLA RHOMBOIDEA N. SP.

Valve rhomboidal, with acute ends; dorsal part one and a half times the

width of the ventral; median line nearly straight, with terminal fissures

turned downwards near the ends; axial area broad, not widened in the

middle, except slightly on the ventral side; striæ {64}radiate, distant in

the middle of the dorsal side where they are 7 in 10 µ, coarsely punctate,

the puncta in longitudinal lines, 9 in 10 µ on the ventral side, closer at

the ends. L. 69 µ.

Baker's Run, Willistown, Pa.

Pl. 18, Fig. 11.

CYMBELLA GRACILIS (RAB.) CL.

Valve semi-lanceolate, with acute ends; median line nearly straight, with

terminal fissures turned downwards, distant from the ends; axial area

linear; ventral margin straight or slightly gibbous in the middle.

Hammonton Pond, N. J.

Pl. 18, Fig. 20.

CYMBELLA LACUSTRIS (AG.) CL.

Valve elliptical-lanceolate, with obtuse ends, nearly symmetrical; median

line straight, terminal fissures distant from the ends; striæ radiate in

the middle, convergent at the ends, coarsely lineate.

Belmar, N. J.

Pl. 18, Fig. 25.

AMPHORA EHR. (1840)

(amphora, a jar)

Valves asymmetrical along the longitudinal axis, as in Cymbella, but with

the plane passing through the dorsal and ventral sides of one valve at an

angle with that of the other. As Cleve states, Cymbella and Amphora are

forms of Navicula "with both valves similar and asymmetrical along the

longitudinal axis," and the difference between Cymbella and Amphora is in

the "degree of asymmetry." If, following H. L. Smith's diagrams (Lens, Vol.

2, 1873, p. 66), we assume that the usual form of the valve in Navicula is

elliptical or lanceolate, and the zone view is rectangular, we have in

Cymbella an arcuate median line and a more or less reniform valve, while

the zone view remains rectangular with the valves parallel. Now, if the

valves are asymmetrical along the longitudinal axis, and one side of one

valve is separated from the corresponding side of the opposite valve by a

wider connective zone than is the case on the other side, the transverse

section of the frustule will appear cuneate, as in Amphora, and the

connective zone will be wider on one side than the other. When, therefore,

we examine an entire frustule as it is usually seen, we shall find the two

raphes of the valves in focus at the same time on the ventral side, and, by

changing the focus, the convex sides of the same valves are seen, the

dorsal view with, usually, a wider connective zone. As an illustration,

compare Figs. 5 and 6, on Plate 15, Fig. 6 being the ventral, and Fig. 5

the dorsal view.

As Amphoræ are epiphytic or parasitic, they are considered, as Cleve

remarks, like Achnanthes and Cocconeis, as "degenerated forms."

Chromatophores usually single, lying on the ventral connective zone.

Mereschkowsky describes nine forms.

Cleve divides the genus into a number of groups as follows:

_Amphora proper._--Connective zone not complex; valves with longitudinal

lines on the dorsal side; coarsely punctate or costate.

_Diplamphora._--Zone complex; otherwise as in Amphora.

_Halamphora._--Longitudinal lines absent; frustule elongate, with

protracted ends.

{65}_Oxyamphora._--Zone complex; longitudinal lines absent; frustule

elliptical; valve lunate, with or without a central stauros; striæ

punctate.

_Amblyamphora._--Zone complex; frustule rectangular; valve lunate; striæ

punctate; axial and central areas indistinct.

_Psammamphora._--Zone not complex; frustule rectangular; central nodule

frequently dilated to a stauros; no axial or central area.

_Cymbamphora._--Valve semi-lanceolate; median line straight, approximate to

the ventral margin.

AMPHORA

AMPHORA ROBUSTA GREG.

Frustule elliptical, truncate; valve lunate, with straight ventral margin;

median line biarcuate; ventral side with coarse, radiate striæ, 6 in 10 µ,

on both sides of the median line.

Along the coast.

Pl. 15, Fig. 1.

AMPHORA PROTEUS GREG.

Frustule elliptical, truncate; valve lunate, with straight ventral margin;

median line biarcuate; no central area. Striæ on the dorsal side not

interrupted, 9 in 10 µ. Ventral side striate toward the ends.

Differs from A. robusta chiefly in size and coarseness of puncta. Extremely

variable in size.

Common along the coast.

Pl. 15, Figs. 5, 6, and 19.

AMPHORA OVALIS (BRÉB.) KUETZ.

Frustule elliptical, truncate; valve lunate; median line biarcuate; striæ

on dorsal side 10-16 in 10 µ.

_Var. libyca (Ehr.) Cl._--Central area distinct on the dorsal side.

_Var. pediculus (Kuetz.) Cl._--Central area and nodule quite distinct.

Striæ finer than in var. libyca.

Common in ponds. Quite variable.

Pl. 15, Fig. 7.

AMPHORA GIGANTEA VAR. FUSCA A. S.

Frustule elliptical; valve lunate, with straight ventral margin. Axial area

absent on the dorsal side; dorsal striæ, 10 in 10 µ, punctate. Ventral part

hyaline except at the ends, which are obliquely striated, with short,

punctate lines. L. 70-120 µ.

Absecon, N. J.

Pl. 38, Fig. 1.

DIPLAMPHORA

AMPHORA CRASSA GREG.

Valve linear-elliptical, with obtuse, incurved ends. Median line biarcuate.

Axial and central areas indistinct on the dorsal side; striæ coarsely

punctate, interrupted by a longitudinal line on the dorsal side.

Along the coast.

Pl. 15, Fig. 3.

{66}AMPHORA AREOLATA GRUN.

Valve with straight ventral margin; median line straight, approximate to

the ventral margin; axial area indistinct; several longitudinal lines

crossed by apparent costæ which alternate with rows of fine puncta.

Blue clay. Rare.

Pl. 15, Fig. 11.

HALAMPHORA

AMPHORA COFFÆIFORMIS (AG.) KUETZ.

Frustule lanceolate, truncate; zone with numerous divisions. Valve arcuate

on the dorsal and nearly straight on the ventral side; ends protracted or

slightly capitate.

_A. aponina_ Kuetz.

_A. salina_ Wm. Sm.

Along the coast.

Pl. 15, Figs. 8 and 18.

OXYAMPHORA

AMPHORA LINEOLATA EHR.

Frustule membranaceous, elliptical, truncate, with broad ends. Zone with

numerous divisions. Dorsal part striated transversely; ventral side with

longitudinal lines.

_A. plicata_ Greg.

_A. hyalina_ H. L. Smith, Type No. 64.

Along the coast.

Pl. 15, Figs. 9 and 10.

AMPHORA OSTREARIA BRÉB.

Frustule oblong, with rounded angles. Zone with five or more divisions

transversely striated. Central area narrow, biarcuate; central nodule

dilated to a stauros. Valve narrow, with arcuate dorsal and straight

ventral margin, acute at the ends. Striæ transverse, finely punctate.

_A. vitræa_ Cl.; _A. porcellus_ Kitton; _A. quadrata_ Bréb.; _A. elegans_

Greg. Appearance varies according to the position of the valve.

Along the coast.

Pl. 15, Figs. 12 and 21.

AMPHORA LÆVIS GREG.

Frustule oblong, hyaline and membranaceous. Valve linear or slightly

arcuate, with ventral margin tumid in the middle; ends obtuse; central

nodule dilated to a stauros; median line very narrow, biarcuate, coinciding

with the dorsal margin at the ends; striæ transverse, punctate.

Blue clay.

Pl. 15, Fig. 13.

AMPHORA ACUTA GREG.

Valve lunate, with acute ends; ventral margin straight; ventral side very

narrow. Central nodule dilated to a stauros; striæ transverse, punctate.

Along the coast.

Pl. 15, Fig. 20.

{67}AMBLYAMPHORA

AMPHORA OBTUSA GREG.

Frustule rectangular. Valve linear, obliquely rounded at the ends, with

arcuate dorsal, and straight ventral, margin; median line biarcuate; striæ,

18-20 in 10 µ.

Along the coast. Common.

Pl. 15, Fig. 4.

PSAMMAMPHORA

AMPHORA ARENARIA DONK.

Frustule hyaline, rectangular, slightly tumid in the middle, with rounded

angles. Valve linear with broad ventral side and straight or sinuate

ventral margin. Striæ, 24-27 in 10 µ (Cleve).

Common along the coast.

Pl. 15, Fig. 17.

The distinction between A. obtusa and A. arenaria is not always evident if

the valves alone are seen. The former has a complex zone, the latter a

simple zone, and the valve has finer striæ. Cleve's descriptions and

references in regard to these two forms do not agree with the descriptions

and figures of H. L. Smith, or with the figures of Schmidt. The valves of

most Amphoræ are capable of assuming various outlines according to their

position.

AMPHORA OCELLATA VAR. CINGULATA CLEVE

Frustule rectangular. Valve linear, with dorsal margin arcuate and the

ventral margin straight. Central nodule with a stauros on the dorsal side.

Squan River, N. J.

Pl. 15, Figs. 14 and 15.

CYMBAMPHORA

AMPHORA ANGUSTA VAR. EULENSTEINII GRUN.

Valve lanceolate, acute at the ends. Median line straight, approximate to

the margin. Axial area widened on the dorsal side, indistinct on the

ventral; striæ punctate.

_A. eulensteinii_ A. S.

Common along the coast.

Pl. 15, Fig. 16.

On Pl. 40, Figs. 21, 22, and 23, I have attempted, imitating H. L. Smith's

figures (Lens, l.c.), to illustrate the difference in the transverse

sections of Navicula, Cymbella and Amphora.

Fig. 21 represents the transverse section of a convex Navicula, in which

the valves ecg and fdh are parallel, and the median nodules c and d are

central.

Fig. 22 is a transverse section of Cymbella in which the valves are nearly

parallel and the median nodules are excentric. The girdles on one side, ea

and af, are narrower than gb and bh on the other side.

Fig. 23 is a transverse section of an Amphora in which the valves appear in

zone view with the median nodules of both valves on the same side. The

girdles on the ventral side, ea and af, are narrower than gb and bh on the

dorsal side. The girdles on the dorsal side are seldom as broad as gb and

bh, the valve extending over a great part of the dorsal side to g' and h'.

{68}AMPHIPRORA EHR. (1843)

(amphi, on both ends, and prora, a prow)

Frustule twisted in the longitudinal axis, constricted in the middle; zone

complex, with numerous divisions crossed by fine striæ. Valve lanceolate,

acute. The raphe confined within a sigmoid keel or extension of the valve;

the central and terminal nodules indistinct. Striæ transverse, punctate,

with coarser striæ at the junction of the keel and lower part of the valve.

Chromatophores single, with indented border except in A. pulchra, in which

there are two chromatophores with entire borders.

AMPHIPRORA ALATA KUETZ.

Frustule with a row of puncta at the junction line. Valve linear, acute at

the ends. Median line sigmoid. Striæ lineate on the lower part of the

valve, punctate on the keel.

Along the coast. Not common.

Pl. 14, Fig. 3.

AMPHIPRORA PULCHRA BAIL.

Frustule with sigmoid connective zone. Valve very convex, with sinuate keel

and junction lines evident. In zone view and in valve view, one half of the

frustule, owing to the elevation of the keel, is wider than the other half.

Striæ punctate, coarser on the keel.

Not uncommon along the coast.

Pl. 14, Figs. 1 and 2.

AMPHIPRORA CONSPICUA GREV.

Valve linear or elliptical, with acute ends. Median line sigmoid, but the

junction lines not evident. Striæ lineate, with coarser lines near the

middle.

Not common. Port Penn, Delaware River.

Pl. 14, Fig. 4.

AMPHIPRORA ORNATA BAIL.

Frustule membranaceous, constricted in the middle, with well-marked folds

extending from the junction line in both directions. Valve lanceolate,

constricted in the middle and with protracted ends. Keel undulate on the

edge.

A beautiful, transparent and delicate form, the only fresh-water species in

our locality.

Delaware Water Gap, Pa.

Pl. 14, Figs. 6 and 7.

AMPHIPRORA PALUDOSA WM. SM.

Frustule membranaceous, constricted, with truncate ends. Valve linear, with

acute ends. Striæ scarcely visible.

Cape May (Cleve).

Pl. 14, Fig. 5.

TROPIDONEIS CLEVE (1891)

(tropis, a keel)

Frustule oblong, constricted in the middle; keel not sigmoid. Axial area

not evident. Striæ very fine, punctate, in longitudinal lines.

{69}TROPIDONEIS LEPIDOPTERA (GREG.) CLEVE

Valve with straight, median excentric line. Keel unilateral, projecting

above the median line in zone view; central area small. Transverse striæ

finely punctate. As usually seen, the valve is inclined. According to

Karsten there are two chromatophores on the connective zone, each divided

into four parts, each of which contains a large oval pyrenoid.

_Amphiprora lepidoptera_ Greg.

Along the coast.

Pl. 14, Figs. 8 and 9.

AURICULA CASTRACANE (1873)

(auricula, the ear, the shape of the valve)

Frustule globose. Valve reniform or cymbiform, elevated into a keel which

is not sigmoid. Median line biarcuate. Differs from Amphiprora in not

having a sigmoid keel.

AURICULA MUCRONATA (H. L. SMITH) PERAGALLO

In zone view, the median line deeply bisects the longitudinal axis, ending

in a mucronate central nodule. Connective zone complex. Valve very complex,

with ventral margin nearly straight and raphe excentric. Central nodule

near the margin, terminal nodules small. Striæ, 35-40 in 10 µ (Cleve).

Chromatophore single, on the ventral part.

_Amphora mucronata_ H. L. Smith.

_Amphora (?) insecta_ Grun.

_Auricula insecta_ (Grun.) Cleve.

"A rare and very curious pelagic species" (Peragallo, Diat. Villefranche).

Prof. H. L. Smith included this form in his first century of "Species

Typicæ Diatomacearum," which was issued prior to 1876, the date of

publication, in Schmidt's Atlas, of Amphora insecta Grun.

Atlantic City, N. J. Rare.

Pl. 15, Fig. 2.

SCOLIOTROPIS CLEVE (1894)

(scolios, twisted, and tropis, a keel)

Frustule linear, oblong. Median line sigmoid near the ends. Valve with

transverse costæ alternating with two intermediate rows of puncta in

oblique lines.

SCOLIOTROPIS LATESTRIATA VAR. AMPHORA CLEVE

Valve asymmetrical, with the median line curved. Frustule sub-acute at the

ends. Median lines not on the same side of each valve of the frustule.

Abundant at Cape May, N. J. Not common elsewhere.

Pl. 14, Figs. 10 and 11.

GOMPHONEIS CLEVE (1894)

(gomphos, a peg, and neis (naus))

Valve elongated, asymmetrical to the transverse axis; axial area narrow;

central area rounded, stigmatic; striæ radiating, costæ alternating with

double rows of fine puncta. An indistinct, longitudinal line near the

border.

Chromatophores and conjugation have not been determined.

{70}GOMPHONEIS HERCULANEUM (EHR.) CL.

Valve clavate, with rounded apex; costæ, 13 in 10 µ, alternating with

double rows of fine puncta, 22 in 10 µ, in oblique rows; axial area narrow,

central area rounded, with one stigma.

_Gomphonema capitatum_ Ehr var. _herculaneum_ Ehr., H. L. S., Type Slide

No. 177.

Common in the blue clay.

Pl. 19, Fig. 2.

Pl. 38, Fig. 15, zone view of young frustule.

GOMPHONEIS MAMILLA (EHR.) CL.

Valve lanceolate, with rounded apex and base; striæ costate, 10 in 10 µ,

alternating with double rows of fine puncta; axial area linear, sometimes

oblique, central area small, with one or more stigmas.

Blue clay. Rare.

Pl. 19, Fig. 1.

In one frustule I noticed one valve with one stigma and the other with four

stigmas.

The difference between G. mamilla and G. elegans is not very great. In the

latter the central area is larger and the longitudinal lines not so near to

the margin. The stigmas form a circlet. There appears to be a coincidence

in the relation of Gomphoneis to Gomphonema, and that of the true

Achnanthes to the group described by Cleve under Achnanthidium. In

Gomphoneis and Achnanthes the striation is both costate and punctate while

in Gomphonema and Achnanthidium the striation is punctate only.

GOMPHONEMA AG. (1824)

(gomphos, a peg, and nema, a filament)

Valve elongated, asymmetrical with respect to the transverse axis; striæ

transverse, usually radiate, punctate.

Chromatophore band single, the middle lying on one zone.

In conjugation, according to Thwaites and Pfitzer, from two mother cells,

which do not form a positive union, two auxospores are developed parallel

to the original frustules. In Plate 19, Fig. 19, I have drawn a

representation of the auxospore formation as I have frequently observed it

in a gathering sent me by Mr. T. C. Palmer, containing G. angustatum, a

common species in this locality. The sagittal plane of the valve of the

auxospore is at right angles to the plane of the valve of the mother cell.

Two valves of one of the mother cells are seen separated, one on each side

of the auxospore which is nearly twice the length of the original

frustules. The two valves of the other mother cell are not shown as they

are not usually found closely united. In the figure one valve alone of the

auxospore is seen, the opposite valve not being in focus. The valves of the

auxospore are usually more or less arcuate, as in Cymbella, to which the

genus is closely allied.

Grunow divides Gomphonema into two groups, Asymmetricæ and Symmetricæ,

according to the presence or absence of stigmas. Cleve suggests Stigmaticæ

and Astigmaticæ as more suitable in order to agree with the Cymbellæ. The

Stigmaticæ are found chiefly in fresh water, sometimes in brackish. All of

the marine forms belong to the Astigmaticæ, which, however, include some

common fresh-water forms. Many species of Gomphonema are stipitate, some

occur in gelatinous masses, and others are free.

{71}GOMPHONEMA MONTANUM SCHUM.

Valve slightly biconstricted, with obtuse apex and basis, somewhat cuneate;

axial area linear, widened in the middle unilaterally; stigma, one; striæ

about 11 in 10 µ, more distant in the middle, punctate.

_Gomphonema subclavatum_ var. _montana_ (Schum.) Cl.

Pavonia, N. J., artesian well. Rare.

Pl. 19, Fig. 3.

GOMPHONEMA GEMINATUM LYNG.

Valve biconstricted, with large, rounded, sub-truncate apex and broad,

sub-truncate basis; striæ, 9 in 10 µ, radiate in the middle, alternately

longer and shorter, transverse at the basis and near the apex where they

again radiate, coarsely punctate, puncta, 12 in 10 µ. Axial area linear;

central area rounded, with several large stigmas in a longitudinal row;

terminal fissures hook-shaped.

Blue clay.

Pl. 19, Fig. 4.

GOMPHONEMA LANCEOLATUM VAR. INSIGNIS (GREG.) CL.

Valve lanceolate; axial area narrow; central area unilateral with one

stigma; striæ with coarse and distant puncta.

Common and variable.

_Gomphonema insigne_ Greg.

Pl. 19, Figs. 6 and 12.

Fig. 12 shows a unilateral central area. Fig. 6 is more clavate in outline

with small central area. In both forms the coarse puncta are in distinct

longitudinal lines in the middle.

GOMPHONEMA ACUMINATUM VAR. TURRIS (EHR.) CL.?

Valve clavate, with cuneate, acute apex; axial area distinct; central area

unilateral with one stigma.

Blue clay.

Pl. 19, Fig. 11.

GOMPHONEMA ACUMINATUM VAR. TURRIS (EHR.) CL.

Valve clavate, with cuneate apiculate apex and narrow basis; axial area

narrow, with a unilateral central space; stigma opposite the short striæ;

striæ more radiate in the upper part, distant in the middle.

Smith's Island, Delaware River.

Pl. 19, Fig. 5.

GOMPHONEMA ACUMINATUM VAR. CORONATA (EHR.) CL.

Valve twice constricted, with broad, cuneate apex; striæ radiate in the

middle, convergent near the apex and radiate at the apex. Variable in size

and outline.

Blue clay. Fresh water. Common.

Pl. 19, Fig. 7.

GOMPHONEMA ACUMINATUM VAR. TRIGONOCEPHALA (EHR.) CL.

Valve broad, with cuneate apex; axial area narrow; central area unilateral

with one stigma.

Pavonia, N. J., artesian well.

Pl. 19, Fig. 20.

{72}GOMPHONEMA CONSTRICTUM EHR.

Valve clavate, constricted beneath the abruptly rounded apex, gibbous in

the middle, striæ alternately longer and shorter; axial area narrow,

central area unilateral, with one stigma.

Common in fresh water.

Pl. 19, Fig. 8.

GOMPHONEMA SPHÆROPHORUM EHR.

Valve clavate, with capitate or rostrate-capitate apex and narrow basis;

axial area very narrow; central area small, unilateral, with one stigma.

Common in fresh water.

Pl. 19, Figs. 9 and 10. Fig. 10 appears to be a transitional form having a

more distinct axial area and rostrate apex.

GOMPHONEMA AUGUR EHR.

Valve broadly clavate, truncate and apiculate at the apex; basis sub-acute;

axial area distinct; central area small, unilateral with one stigma; striæ

with distant puncta.

Blue clay. Willistown, Pa.

Pl. 19, Fig. 21.

GOMPHONEMA INTRICATUM KUETZ.

Valve narrow, lanceolate, slightly gibbous in the middle; axial area

distinct; central area transverse with one stigma; striæ parallel. Quite

variable.

Common in fresh water.

Pl. 19, Fig. 14.

GOMPHONEMA ANGUSTATUM KUETZ.

Valve lanceolate, with sub-rostrate apex and basis; axial area indistinct;

central area unilateral, with one small stigma; striæ slightly radiate,

indistinctly punctate.

Very common in fresh water.

Pl. 19, Figs. 18 and 19.

Fig. 19, as stated above, represents the formation of an auxospore.

GOMPHONEMA ÆQUALE GREG.

Valve linear-lanceolate, nearly symmetrical, with capitate apex and basis;

axial area narrow; central area unilateral, with one stigma; striæ radiate

in the middle, slightly convergent at the ends.

_Gomphonema intricatum var. æquale_ (Greg.) Cl.

Blue clay. Not common.

Pl. 19, Fig. 15.

GOMPHONEMA SARCOPHAGUS GREG.

Valve linear, irregular in outline, with rounded apex and basis; axial area

distinct; central area small, unilateral, with one stigma; striæ irregular

with coarse, distinct puncta.

Occasional in fresh water.

Pl. 19, Fig. 16.

GOMPHONEMA CAPITATUM EHR.

Valve clavate, broad at the sub-truncate apex and slightly constricted, or

with parallel margins; axial area linear, central area stellate, with one

stigma; striæ in the middle alternately longer and shorter.

Blue clay.

Pl. 19, Fig. 22.

{73}GOMPHONEMA PARVULUM VAR. MICROPUS (KUETZ.) CL.

Valve clavate, with rounded apex and basis; axial area indistinct; central

area unilateral, with a small stigma; striæ distant in the middle.

Common.

Pl. 19, Fig. 17.

GOMPHONEMA VENTRICOSUM GREG.

Valve clavate, with broad apex and produced, rounded basis; axial area

narrow, widened in the middle; stigma one; striæ distant in the middle,

finely punctate.

Blue clay.

Pl. 19, Fig. 13.

GOMPHONEMA OLIVACEUM LYNG.

Valve clavate, with broad apex and narrow basis; axial area very narrow;

central area irregular, without stigma; striæ radiate, finely punctate.

Very common.

Pl. 19, Fig. 23.

GOMPHONEMA BRASILIENSE VAR. DEMERARÆ GRUN.?

Valve lanceolate, with sub-cuneate apex and narrowed basis; axial area

lanceolate, broad; no stigma; median fissures remote; striæ parallel, 12 in

10 µ, punctate, the puncta obsolescent, small or interrupted.

Willistown, Pa. Rare.

Pl. 19, Fig. 24.

PLEUROSIGMA WM. SM. (1852)

(pleura, a side, and sigma, the letter s)

Valve lanceolate, sigmoid; axial area very narrow, central area small;

striæ punctate, in transverse and oblique lines.

Cleve divides the forms usually known as Pleurosigma into two genera,

Pleurosigma and Gyrosigma. Pleurosigma includes all forms having oblique

rows of puncta, while Gyrosigma includes all having longitudinal rows. Both

have transverse striæ. The former consists entirely of marine species,

while in the latter the species are found in fresh, brackish and salt

water.

The endochrome in Pleurosigma, according to Mueller, consists of two bands

which differ in the median part of each valve. Mereschkowsky says that the

endochrome is so divided as to form four bands, two on each valve, that

their position is different in different species, and that they are not the

same on valves of the same frustule.

Cleve prefers to classify the species of Pleurosigma and Gyrosigma in

accordance with the outline of the valve and the flexure of the median

line. I shall, however, retain the method used by Peragallo and Grunow and

arrange the forms according to the striation.

(1) OBLIQUE STRIÆ ABOUT 90 DEGREES, MORE DISTINCT THAN THE TRANSVERSE

PLEUROSIGMA FORMOSUM WM. SM.

Valve elongated, slender, gently sigmoid, acute at the ends; oblique striæ

crossing each other at about 90 degrees; 10-16 in 10 µ; transverse striæ,

14-20 in 10 µ (Cleve).

Along the coast.

Pl. 22, Fig. 5.

{74}PLEUROSIGMA OBSCURUM WM. SM.

Valve linear, not sigmoid, or scarcely so; ends obtuse, subconical; raphe

sigmoid, near the margin at the extremities; transverse and oblique striæ

equidistant, 28 in 10 µ (Wm. Sm.).

Abundant at Greenwich Point, Philadelphia.

Pl. 22, Fig. 4.

(2) OBLIQUE STRIÆ CLOSER AT THE ENDS

PLEUROSIGMA NAVICULACEUM BRÉB.

Valve lanceolate, slightly sigmoid at the extremities; raphe strongly

sigmoid near the margin at the ends; central nodule large, rounded; oblique

striæ, 13-14 in the middle, closer at the ends; transverse striæ, 18-20 in

10 µ (Peragallo).

Long Island Sound.

Pl. 22, Fig. 6.

PLEUROSIGMA VIRGINIACUM H. L. SMITH

Valve slightly sigmoid, with acute ends; raphe more sigmoid than the valve,

excentric near the ends; oblique striæ in different directions at the

centre, 13 in 10 µ, closer and less distinct at the ends; central nodule

small but prominent because of its thickness, producing by diffraction an

apparently wide area (somewhat exaggerated in the figure). L. 95 µ, usually

larger.

_P. affine_ var. _fossilis_ Grun. (Peragallo).

_P. normanii_ var. _fossilis_ Grun. (Cleve).

Common in the blue clay.

Pl. 22, Fig. 8.

(3) OBLIQUE STRIÆ 60 DEGREES

PLEUROSIGMA ANGULATUM (QUEKETT) CL.

Valve rhomboidal, with sub-rostrate or produced ends; central nodule

rhomboidal; raphe central; transverse and oblique striæ at an angle of 60

degrees, equidistant, 18-22 in 10 µ.

_Navicula angulata_ Quekett.

Along the coast.

Pl. 22, Fig. 3.

PLEUROSIGMA STRIGOSUM WM. SM.

Valve lanceolate, with sub-acute, somewhat revolute, apices; oblique striæ

at an angle of about 60 degrees, otherwise as in angulatum.

Along the coast. Not common.

Pl. 22, Fig. 1.

PLEUROSIGMA ÆSTUARII BRÉB.

Valve lanceolate, with produced apices; raphe less sigmoid than the valve

and excentric; oblique striæ, 19-21 in 10 µ, at an angle of about 60

degrees.

Along the coast. Common.

Pl. 22, Fig. 7.

{75}(4) OBLIQUE STRIÆ 60 DEGREES, THE TRANSVERSE MORE DISTANT

PLEUROSIGMA RIGIDUM WM. SM.

Valve nearly straight or slightly sigmoid, with obtuse ends; raphe central,

excentric near the ends; oblique striæ, 17-21, transverse, 16-19 in 10 µ.

(Peragallo).

New Rochelle, N. Y.

Pl. 22, Fig. 2 (very near the var. gigantea Grun.)

GYROSIGMA HASSALL (1845)

(gyros, curved, and sigma)

Valve lanceolate, sigmoid; axial area very narrow, central area small;

striæ punctate, in transverse and longitudinal rows.

Chromatophores two, in long and narrow bands, perforated, differing from

those of Pleurosigma. The elæoplasts are also arranged differently in the

two genera. (Mereschkowsky, Études sur l'Endochrome des Diatomées, Imperial

Academy of Petrograd, 1901, Vol. 11, No. 6, p. 18 et seq.)

The arrangement is according to Peragallo.

(1) LONGITUDINAL STRIÆ MORE DISTANT THAN THE TRANSVERSE

GYROSIGMA HIPPOCAMPUS (EHR.)

Valve lanceolate, sigmoid, with obtuse ends; raphe nearly central;

transverse striæ 15-17, longitudinal, 10-12 in 10 µ.

_Navicula hippocampus_ Ehr.

_Pleurosigma hippocampus_ (Ehr.) Wm. Sm.

_Gyrosigma attenuatum_ (Kuetz.) Cl.

Long Island Sound.

Pl. 23, Fig. 3.

(2) LONGITUDINAL AND TRANSVERSE STRIÆ NEARLY EQUAL

GYROSIGMA BALTICUM (EHR.) CL.

Valve with margins parallel nearly to the extremities, which are suddenly

unilaterally sub-conical and obtuse; raphe sigmoid; transverse and

longitudinal striæ nearly equally distant, 15 in 10 µ (Per.). L. 200-360 µ.

_Navicula baltica_ Ehr.

_Pleurosigma balticum_ (Ehr.) Wm. Sm.

Common along the coast.

Pl. 23, Fig. 2.

GYROSIGMA PARKERI VAR. STAURONEIOIDES GRUN.

Valve lanceolate, slightly sigmoid, ends produced into beaks with sub-acute

apices; raphe straight in the middle part; central nodule elliptical;

transverse striæ, 21, and longitudinal, 24 in 10 µ (Per.).

An apparent stauros, variable in width, extends to the margin and, in

consequence, the median transverse striæ are more evident. L. 75 µ.

Schuylkill River. Rather rare.

Pl. 23, Fig. 7.

{76}GYROSIGMA SIMILE (GRUN.)

Valve slightly sigmoid, broad, with obtuse ends; raphe sigmoid, nearly

central; transverse striæ, 15, longitudinal, 16-17 in 10 µ (Per.).

_Pleurosigma simile_ Grun.

_Gyrosigma balticum_ var. _similis_ (Grun.) Cl.

Shark River, N. J.

Pl. 23, Fig. 4.

(3) TRANSVERSE STRIÆ MORE DISTANT

GYROSIGMA ACUMINATUM (KUETZ.) CL.

Valve sigmoid, tapering to the sub-acute ends; raphe central; transverse

and longitudinal striæ nearly equally distant, 17 or 18 in 10 µ (Per.).

_Frustulia acuminata_ Kuetz.

Port Penn, Delaware River.

Pl. 23, Fig. 5.

GYROSIGMA STRIGILIS (WM. SM.) CL.

Valve sigmoid, with obtuse ends; raphe doubly sigmoid; axial area rather

wide; transverse striæ, 13, and longitudinal, about 16 in 10 µ.

Long Island Sound. Not common.

Pl. 23, Fig. 1.

GYROSIGMA KUETZINGII (GRUN.) CL.

Valve sigmoid, lanceolate, with sub-acute ends; raphe central, the central

nodule elliptical; transverse striæ, 21-23, and longitudinal, 25-26 in 10

µ.

_Pleurosigma spencerii_ var. _acutiuscula_ Grun.

_Pleurosigma spencerii_ var. _kuetzingii_ Grun.

Common in fresh water.

Pl. 38, Fig. 12.

GYROSIGMA SCALPROIDES (RAB.) CL.

Valve slightly sigmoid, with obtuse ends; raphe nearly straight; central

nodule elliptical; transverse striæ, 22, slightly radiate and more distant

in the middle; longitudinal striæ, 29 in 10 µ. L. 60 µ.

Common in streams.

Pl. 38, Fig. 9.

In Pl. 23, Fig. 6 represents a form more sigmoid.

GYROSIGMA SPENCERII VAR. NODIFERA GRUN.

Valve sigmoid, with obtuse ends; raphe central; central nodule obliquely

elongated; transverse striæ, 17-18 in 10 µ, curved in the middle of the

valve, longitudinal striæ, 22 in 10 µ. L. 150 µ.

Blue clay.

Pl. 23, Fig. 8.

GYROSIGMA PROLONGATUM (WM. SM.) CL.

Valve narrow, lanceolate, produced into beaks, curved in a contrary

direction; raphe central; transverse striæ, 20-21 in 10 µ, longitudinal

closer. L. 140 µ.

Along the coast, northward.

Pl. 38, Fig. 13.

I have not seen any specimens south of New England, but they will probably

occur.

{77}(4) STRIÆ ALIKE, EXTREMITIES PRODUCED

GYROSIGMA FASCIOLA (EHR.) CL.

Valve lanceolate, attenuated into curved beaks turned in opposite

directions; raphe central, straight, except at the beaks; transverse striæ,

22, longitudinal, 24 in 10 µ (Per.).

New York Bay.

Pl. 23, Fig. 9.

FRUSTULIA AG. (1824); em. GRUN. (1865)

(frustulum, a small piece)

Valves naviculoid, similar, usually free but sometimes enclosed in

gelatinous tubes or embedded in mucus. Median line between two thickened

ribs. Central and terminal nodules frequently elongated. Surface of valve

with fine puncta in longitudinal and transverse lines appearing hyaline

under medium powers.

Chromatophores, two, extending along the girdle. They differ from those of

Navicula in being separated from the wall in the middle by a hemispherical

mass of protoplasm. According to Pfitzer, each chromatophore is divided in

the middle, allowing a connection between the hemispherical mass and the

central plasma mass. Schmitz states that the chromatophore is thickened in

the middle and contains a pyrenoid.

In conjugation, two frustules form two cylindrical bodies which later

become conical and from which are formed the sporangial valves twice the

usual size.

FRUSTULIA LEWISIANA (GREV.) DE TONI

Valve elliptical or linear, with rounded ends; terminal nodules elongated,

at a distance from the ends; striæ, 24 in 10 µ.

Port Penn, Delaware River. Along the coast.

Pl. 17, Fig. 1.

FRUSTULIA RHOMBOIDES (EHR.) DE TONI

Valve lanceolate or rhombic-lanceolate, rounded at the ends; central and

terminal nodules short; striæ, 20 in 10 µ, sometimes coarser.

Common in fresh water.

Pl. 17, Fig. 2.

FRUSTULIA RHOMBOIDES VAR. AMPHIPLEUROIDES GRUN.

Valve rhombic-lanceolate; central and terminal nodules elongated; median

line somewhat excentric.

Blue clay.

Pl. 17, Fig. 3.

FRUSTULIA RHOMBOIDES VAR. SAXONICA (RAB.) DE TONI

Valve smaller than in rhomboides, with somewhat produced ends, closer

median ribs and rounded central nodule.

Fresh water.

Pl. 17, Fig. 6.

FRUSTULIA VULGARIS (THWAITES) DE TONI

Valve elliptical-lanceolate, with rounded or sometimes sub-rostrate ends;

central and terminal nodules slightly elongated; striæ delicate, closer at

the ends. Frustules at first in gelatinous tubes.

_Colletonema vulgaris_ Thwaites.

Fresh water.

Pl. 17, Fig. 4.

{78}FRUSTULIA INTERPOSITA (LEWIS) DE TONI

Valve linear-elliptical, rounded at the ends; terminal nodules short.

_Navicula interposita_ Lewis.

Along the coast. Port Penn, Delaware River.

Pl. 17, Fig. 5.

AMPHIPLEURA KUETZ. (1844)

(amphi, on both sides, pleura, a side)

Frustules free, in gelatinous masses or in tubes. Valve linear-lanceolate;

central nodule narrow, extending half the length of the valve or more, then

forking toward the ends. Terminal nodules prolonged, as in Frustulia, into

a "porte-crayon-shaped" figure.

Chromatophores two, very short.

AMPHIPLEURA PELLUCIDA KUETZ.

Frustules free or in mucous masses. Valve fusiform; forks about one-fourth

the length of the valve; striæ transverse, punctate, 36-40 in 10 µ (J. J.

Woodward).

Occasional in the Delaware River.

Pl. 17, Fig. 9.

AMPHIPLEURA RUTILANS (TRENTEPOHL) CL.

Frustules enclosed in gelatinous tubes. Valve linear-lanceolate, obtuse at

the ends; forks about one-third the length of the valve; striæ, 28 in 10 µ.

_Conferva rutilans_ Trentepohl.

_Schizonema dillwynii_ Wm. Sm.

Abundant at Belmar, N. J.

Pl. 17, Fig. 10.

Fig. 11 represents a portion of the gelatinous tube containing frustules.

DICTYONEIS CLEVE (1890)

(dictyon, a net)

Frustules oblong. Valve lanceolate, constricted in the middle (in our

species); an outer layer finely punctate and an inner layer of

reticulations; the margin of the valve divided into large, quadrate cells.

The genus Dictyoneis includes species at one time ascribed to Mastogloia

and Navicula. The structure, however, is not like that of either, as the

loculi are attached to the valve and are not separable as in Mastogloia,

and the cell-wall is not like that of any Navicula.

Cleve remarks that Dictyoneis is found in warm waters. Lewis found one

specimen at Black Rock Harbor, L. I., and one in the Delaware River blue

clay. The specimens here described I found living on the New Jersey coast.

DICTYONEIS MARGINATA VAR. TYPICA CLEVE

Valve panduriform, with cuneate lobes; axial area narrow, linear, scarcely,

or not at all, widened in the middle; terminal fissures in contrary

directions; outer stratum finely punctate, about 25 in 10 µ, in parallel

striæ; inner stratum coarsely reticulated. Four and one-fourth times longer

than broad; marginal cells, 5 in 10 µ, smaller or obsolescent in the middle

of the valve; cells of the valve in irregular transverse rows, 10-12 in 10

µ. L. 93 µ.

_Navicula marginata_ Lewis.

Absecon, N. J.

Pl. 20, Fig. 3.

{79}DICTYONEIS MARGINATA VAR. COMMUTATA CLEVE

Valve four and one-half times longer than broad; cells of the valve in

irregular, transverse rows about 11 in 10 µ; marginal cells nearly equal, 6

in 10 µ. L. 125 µ.

Absecon, N. J.

Pl. 20, Fig. 2.

DICTYONEIS MARGINATA VAR. MAXIMA N. VAR.

Valve with cuneate segments; marginal cells, 4 in 10 µ; cells of the valve,

5 in 10 µ, obsolescent in the middle and smaller; transverse striæ, 25 in

10 µ.

Atlantic Coast. Rare.

Pl. 20, Fig. 1 (from a specimen found at Colon).

TRACHYNEIS CLEVE (1894)

(trachys, rough, and neis (naus), named from the chief species)

Valve more or less linear or linear-lanceolate. It appears to be composed

of three strata, one an interior, coarsely dotted, an exterior of fine

puncta in longitudinal striæ, scarcely visible, and a median of transverse

anastomosing costæ forming irregular alveoli.

Chromatophores, two or four bands on the zone (Mereschkowsky).

TRACHYNEIS ASPERA VAR. INTERMEDIA GRUN.

Valve linear-elliptic; axial area a stauros widened outward and unilateral.

Striæ of the median layer of radiating rows of oblong alveoli.

Along the coast. Not common.

Pl. 17, Fig. 15.

The type form and its numerous varieties are quite ubiquitous. Very large

specimens occur in the Antarctic regions, especially in material from Ross

Island, S. Victoria Land (Shackleton Ant. Exp.).

BRÉBISSONIA GRUN. (1860)

(named after Alphonse de Brébisson, the distinguished French naturalist)

Frustules stipitate; valve lanceolate; striæ transverse in the middle,

radiate at the ends. Median area narrow, central nodule elongated, terminal

fissures at a distance from the ends. Valve with an outer finely punctate

stratum.

At one end of one valve in each frustule is found a conspicuous punctum,

the plasma pore of Otto Mueller, through which the frustule is connected

with the gelatinous stipe, analogous to the pore in Diatoma connecting the

zig-zag frustules.

Chromatophore single, lying on one girdle and passing over to each valve.

BRÉBISSONIA BOECKII (KUETZ.) GRUN.

Valve lanceolate, with sub-acute apices; striæ, 3-4 in 10 µ, not reaching

the median line.

Blue clay. Very rare. Common in brackish water at Chestertown, Md. (T. C.

Palmer)

Pl. 17, Fig. 7.

{80}BRÉBISSONIA PALMERII, N. SP.

Valve rhombic-lanceolate, with cuneate ends and produced apices. Central

nodule more elongate and terminal fissures further from the ends than in B.

boeckii.

Pavonia, N. J. (artesian well, depth of 40 ft.). Rare.

Pl. 17, Fig. 8.

I take pleasure in naming this species after Mr. T. Chalkley Palmer, of

Media, Pa., the author of numerous papers on the Diatomaceæ.

Lewis partly describes a similar form, which he does not name, as a species

of Navicula found in the blue clay at Kaighn's Point, N. J. (Lewis, "New

and Intermediate Forms," etc., p. 15, Pl. 1, Fig. 8.)

ANOMOEONEIS PFITZER (1871)

(anomoios, unlike, and neis (naus), a boat)

Valve lanceolate, axial area narrow, central area widened; transverse striæ

punctate, the puncta in longitudinal rows or interrupted by blank lines.

A single chromatophore lies along one of the girdle sides and extends over

the valves, each of the two parts being deeply notched or slit at the ends.

According to Schmitz there are two pyrenoids, but Heinzerling thinks there

is but one.

Cleve considers this genus not well founded, as it is based upon the cell

contents of but one species, the structure of the other species not being

known. As the forms here described are easily recognized by the interrupted

puncta, the genus is, at least, convenient.

ANOMOEONEIS SPHÆROPHORA (KUETZ.) CL.

Valve elliptic-lanceolate, ends rostrate-capitate. Axial area narrow,

central area rounded, larger on one side of the median line than the other.

Striæ very slightly radiate, 16 in 10 µ, punctate, the puncta interrupted

by longitudinal blank lines.

Pfitzer states that the central plasma mass is unequal on the two sides.

_Navicula sphærophora_ Kuetz.

Fresh and brackish water. Not common.

Pl. 40, Fig. 2.

ANOMOEONEIS SERIANS (BRÉB.) CL.

Valve lanceolate, acute; axial area lanceolate; striæ, 24 in 10 µ; puncta

elongate.

Not common in this locality, but abundant northwards; fossil in the peat

deposits of New England.

May's Landing, N. J.

Pl. 17, Fig. 12.

Forma minor--Valve rhombic-lanceolate, smaller than the type.

May's Landing, N. J.

Pl. 17, Fig. 13.

ANOMOEONEIS FOLLIS (EHR.) CL.

Valve rhomboid, tumid in the middle and obtuse at the produced ends.

Central area lanceolate; striæ radiate in the middle, transverse at the

ends.

_Navicula follis_ Ehr.

_Navicula trochus_ Kuetz.

{81}Reported by Lewis as very rare in the blue clay of the Delaware River.

I have not seen it in this locality. The figure is drawn from a specimen in

the W. Bridgewater, Mass., deposit.

Pl. 17, Fig. 14.

CALONEIS CLEVE (1894)

(calos, beautiful)

Valve convex, linear or lanceolate in general outline, with transverse,

smooth or finely punctate striæ crossed by one or more longitudinal lines.

Endochrome of two chromatophores lying one on each valve, entire in some

species and deeply cleft in others.

CALONEIS LIBER (WM. SM.) CL.

Valve linear, with parallel margins and rounded ends; axial area narrow,

central area orbicular; striæ transverse in the middle, slightly divergent

at the ends, 16 in 10 µ; terminal fissures slightly curved in the same

direction; longitudinal line median. L. 82 µ.

Atlantic coast, chiefly southward.

Pl. 40, Fig. 1.

CALONEIS SILICULA (EHR.) CL.

Valve linear, gibbous in the middle, with broad sub-cuneate ends; axial

area narrow, central area rounded; longitudinal line marginal; striæ

parallel or nearly so, 16 to 18 in 10 µ.

_Navicula silicula_ Ehr.

_Navicula limosa_ Donk.

Blue clay.

Pl. 21, Fig. 3 (var. genuina Cl.).

CALONEIS SILICULA VAR. INFLATA (GRUN.) CL.

Valve gibbous in the middle, with rounded ends; central area elliptical.

Schuylkill River.

Pl. 21, Fig. 4.

C. silicula may be recognized by its yellow color when dry. Its varieties

are extremely numerous.

CALONEIS TRINODIS (LEWIS)

Valve divided into three segments of equal width; ends cuneate and usually

produced; axial area elliptical with a lunate marking on each side; striæ

radiate in the middle, elsewhere parallel, about 20 in 10 µ, finely

punctate; longitudinal line marginal, scarcely visible; the striæ become

fainter toward the axial area.

Occasional in streams and in the blue clay. Abundant in a water-trough at

Ashbourne, Pa.

Pl. 21, Fig. 8.

I have retained Lewis' name as specific. Lewis, wrongly, I think, ascribes

his species to _Navicula trinodis_ Wm. Sm., which is not figured by Smith,

but is illustrated by Van Heurck (Syn. Pl. 14, Fig. 31a), and is named by

Cleve _Navicula contenta_ var. _biceps_ Arnott. {82}De Toni includes Lewis'

name under _Rhoiconeis trinodis_ (Wm. Sm.) Grun. Rhoiconeis is

achnanthiform, with frustules arcuate, and the species is named by Cleve

_Achnanthes trinodis_ (Arnott). _Caloneis schumanniana_ (Grun.) Cl., to

which as a variety Cleve unites Lewis' form, appears to resemble it only in

the lunate marks.

Fig. 9 represents a single specimen found in the Pavonia deposit and which

I believe to be an abnormal form of C. trinodis, differing only in the

degree of inflation and in the larger central area.

_Navicula trinodis_ var. _inflata_ Schultze, from Staten Island, is the

same form figured by Lewis, who states that certain specimens have produced

apices.

CALONEIS PERMAGNA (BAIL.) CL.

Valve lanceolate, with produced apices; median line nearly straight; axial

area lanceolate, irregular or slightly unilateral, about half the width of

the valve; striæ, 9 in 10 µ, radiate and indistinctly punctate;

longitudinal lines double. L. 100-200 µ.

_Pinnularia permagna_ Bail.

Common in brackish water.

Pl. 21, Fig. 1.

CALONEIS PERMAGNA VAR. LEWISIANA N. VAR.

Valve lanceolate, with undulating sides and sub-cuneate apices; axial area

less than one-third the width of the valve; striæ radiate, 12 in 10 µ,

indistinctly punctate; longitudinal lines double, closer together than in

the type. L. 140 µ.

Lewis illustrates this variety in "New and Rare Species," Pl. 2, Fig. 11,

and states that it is probably Navicula esox Kuetzing. This is an error, as

Kuetzing's species is Pinnularia esox Ehr., a form near P. major.

Rather common in the Delaware River.

Pl. 21, Fig. 2.

CALONEIS FORMOSA (GREG.) CL.

Valve lanceolate, with sub-cuneate apices; axial area one-fourth to

one-fifth the width of the valve, somewhat unilateral, dilated in the

middle; striæ, 12-14 in 10 µ radiate, punctate; longitudinal lines double,

distinct. Variable in size and outline.

Abundant along the shores of the Delaware River.

Pl. 21, Fig. 18.

CALONEIS BREVIS VAR. VEXANS (GRUN.) CL.

Valve elliptical-lanceolate; apices obtuse; median fissures distant; axial

area narrow; central area large, orbicular; longitudinal lines close

together, median.

Shark River, N. J.

Pl. 21, Fig. 5.

CALONEIS WARDII CL.

Valve linear, ends cuneate; axial area linear; central area dilated to a

stauros reaching the margin; striæ parallel, radiate at the ends, 18 in 10

µ; longitudinal lines marginal.

Not uncommon in the Delaware River.

Pl. 21, Figs. 6 and 7.

{83}CALONEIS POWELLII (LEWIS) CL.

Valve linear, with cuneate ends; axial area linear; central area large,

quadrate, united to the wide longitudinal lines; striæ parallel, smooth, 8

in 10 µ.

Long Island (Lewis); Smith's Island, Delaware River.

Pl. 21, Fig. 10.

NEIDIUM PFITZER (1871)

(neidion, dim. of naus, a boat)

Valve linear or lanceolate; median fissures turned in opposite directions,

terminal fissures appearing bifurcate (?); striæ transverse, usually

oblique, finely punctate, crossed by one or several longitudinal blank

lines.

Chromatophores, two, lying on the girdle side, in cell division each

forming a partially divided pair. A large pyrenoid is said to be found in

the middle of each chromatophore, but Mereschkowsky states that the

pyrenoids are absent, but that in N. affine four elæoplasts are always seen

in the centre of the frustule.

A genus easily recognized by the peculiar terminal and median fissures and

by the yellowish or brownish color of the valves when dry, darker than in

Caloneis.

NEIDIUM AFFINE (EHR.) PFITZER

Valve linear, with protracted, sub-rostrate or capitate ends.

_Navicula affinis_ Ehr.

NEIDIUM AFFINE VAR. GENUINA FORMA MAXIMA CL.

Striæ, 14 in 10 µ, punctate, oblique in the middle, convergent at the ends;

puncta, 15 in 10 µ. L. 238 µ.

Pensauken, N. J. (artesian well).

Pl. 21, Fig. 11.

Var. genuina forma minor Cl.--L. 26 µ; striæ, 24 in 10 µ.

Brandywine Creek.

Pl. 21, Fig. 12.

NEIDIUM AFFINE VAR. AMPHIRHYNCUS (EHR.) CL.

Valve linear, with protracted capitate ends; striæ transverse, interrupted

by several longitudinal lines.

Willistown, Pa.

Pl. 21, Fig. 13.

NEIDIUM AMPHIGOMPHUS (EHR.) PFITZER

Valve with parallel margins and cuneate ends; striæ transverse, interrupted

by several longitudinal lines; central area widened transversely.

_Navicula amphigomphus_ Ehr.

Wissahickon.

Pl. 21, Fig. 14.

NEIDIUM PRODUCTUM (WM. SM.) CL.

Valve linear, elongate, with capitate apices; striæ slightly oblique;

longitudinal lines marginal; axial area very narrow, central area small.

_Navicula producta_ Wm. Sm.

Newtown Square.

Pl. 21, Fig. 16.

{84}NEIDIUM IRIDIS (EHR.) CL.

Valve linear or lanceolate-elliptical, with sub-cuneate or rounded ends;

striæ oblique, about 18 in 10 µ; central area orbicular.

_Navicula iridis_ Ehr.

_Navicula firma_ Kuetz.

Willistown, Pa.; Middletown, Delaware Co., Pa. (Palmer).

Pl. 21, Fig. 17.

The form here figured is probably the variety ampliata (Ehr.) Cl. with less

acute apices and more elliptical outline. The species occurs in many

variations, the larger being found northward, especially in the peat

deposits of New England.

NEIDIUM HITCHCOCKII (EHR.) CL.

Valve linear, with triundulate margin and cuneate ends; striæ transverse,

oblique.

_Navicula hitchcockii_ Ehr.

Pavonia, N. J. (artesian well); Kirkwood Pond, N. J.

Pl. 21, Fig. 15.

DIPLONEIS EHR. (1840)

(diplos, double)

Valve elliptical or panduriform; median line enclosed in strongly siliceous

horns corresponding to the lyre-shaped areas of Navicula lyra but never

punctate; central nodule, quadrate; valve costate, or striate, or both;

between the horns and the outer part are thinner spaces or sulci, and, in

some species, outside of the sulci are narrow spaces known as lunulæ.

Chromatophores, two, upon the girdle or the valves. Pyrenoids have been

found in one species only, D. interrupta.

DIPLONEIS ELLIPTICA (KUETZ.) CL.

Valve elliptical; central nodule large; sulci narrow, curved, close to the

horns; striæ punctate, in rows radiating more and more toward the ends.

Variable in size and in the coarseness of puncta which are from 10 to 13 in

10 µ (Cleve).

Cleve describes D. ovalis Hilse as having the central nodule rounded, but

otherwise about the same as D. elliptica, and as equivalent to Navicula

ovalis A. Schmidt (Atlas, Pl. 7, Figs. 33 to 36).

Very common in fresh water and occasional in brackish.

Pl. 20, Fig. 14.

DIPLONEIS SMITHII (BRÉB.) CL.

Valve elliptical; central nodule not broad; furrows evenly curved on the

outer edge, crossed by costæ and double oblique rows of alveoli. Variable

in size and in the curvature of the furrows.

Cleve forms a new species, D. major, of the large form figured by Schmidt

(Atlas, Pl. 7, Figs. 18, 19, 21 and 22), stating that the structure is much

coarser and the form is larger with broad furrows. In the specimen here

figured the size is median and the furrows are as in D. major.

Marine and brackish. Common.

Pl. 20, Fig. 17.

{85}DIPLONEIS CRABRO VAR. PANDURA (BRÉB.) CL.

Valve constricted, segments tongue-shaped; central nodule small; horns

narrow, nearly parallel, with a row of large puncta; costæ, 4 in 10 µ,

convergent in the middle, radiating at the ends, alternating with a double

row of puncta, 11 in 10 µ.

Pavonia, N. J. (artesian well).

Pl. 20, Fig. 4.

DIPLONEIS CRABRO VAR. EXPLETA (A. S.) CL.

Valve slightly constricted, segments tongue-shaped; costæ robust, 5 or 6 in

10 µ, alternating with double rows of rather coarse puncta. L. 56 µ.

Port Penn, Delaware River.

Pl. 20, Fig. 15.

DIPLONEIS CRABRO VAR. PANDURELLA CL.?

Valve constricted, the lobes elliptical; central nodule large, with horns

parallel in the middle, convergent at the ends; furrows wide, with faint

costæ; no lunula; costæ parallel in the middle, radiate at the ends, 9 in

10 µ, alternating with very fine double rows of puncta (not shown in the

figure). L. 65 µ.

Blue clay.

Pl. 20, Fig. 13.

DIPLONEIS CRABRO VAR.?

Valve constricted, segments elliptical; costæ, 8 in 10 µ, converging in the

middle, radiating at the ends; horns narrow; furrows wide, costate; lunulæ

indistinct. L. 75 µ.

Resembles var. pandurella except in the convergence of the costæ and in the

lunula.

Squan River. Marine.

Pl. 20, Fig. 9.

DIPLONEIS FUSCA VAR. DELICATA (A. S.) CL.

Valve elliptical; furrows broad, crossed with rows of faint costæ and

alveoli; costæ, 6 or 7 in 10 µ; alveoli, 10 in 10 µ, in short, irregular,

longitudinal rows. L. 84 µ.

Port Penn, Delaware River.

Pl. 20, Fig. 11.

DIPLONEIS GRUENDLERI (A. S.) CL.

Valve constricted, segments tongue-shaped, often unequal; horns broad,

divergent in the middle; furrows narrow; costæ transverse, crossed by from

3 to 7 longitudinal costæ, interrupted in the middle at the border.

Blue clay.

Pl. 20, Figs. 7 and 8.

DIPLONEIS PUELLA (SCHUM.) CL.

Valve elliptical, sometimes orbicular; furrows very narrow; striæ, 20 in 10

µ, indistinct. L. 15 µ.

_Diploneis elliptica_ var. _minutissima_ Grun.

Shark River, N. J. Brackish.

Pl. 20, Fig. 12.

DIPLONEIS EXCENTRICA, N. SP.

Valve elliptical; central nodule quadrate; furrows of the same width

throughout, nearly parallel; costæ radiating toward the ends, 10 in 10 µ,

indistinct on the furrows, alternating with alveoli, 7 in 10 µ, in

irregular, longitudinal lines. One side of the valve is one and a half

times the width of the other. L. 49 µ.

{86}I can find neither description nor figure of any species to which I can

ascribe this form. It approaches D. elliptica. The alveoli are quite

distinct and distant from each other.

Brackish water. Very abundant in a gathering from Squan River, N. J.

Pl. 20, Fig. 10.

DIPLONEIS OCULATA (BRÉB.) CL.

Valve elliptical; striæ radiate at the ends, about 20 in 10 µ, coarsely

punctate. L. 23 µ.

Fresh water.

Pl. 26, Fig. 7.

The figure is drawn from Brébisson's original material in H. L. Smith's

Type Slide No. 299.

_Navicula oculata_ Bréb.

Reported from New Jersey. I have not seen this species in this locality.

Navicula oculata, referred to by Kain as occurring in Shark River, is not

this form.

DIPLONEIS GEMMATA (GREV.) CL.

Valve oblong-linear, with cuneate ends and parallel or slightly concave

sides; central nodule large; horns parallel; furrows about one-third the

width of the valve. Costæ about 5 in 10 µ, alternating with double rows of

fine puncta; short costæ occur along the borders of the horns.

Port Penn, Delaware River.

Pl. 20, Fig. 16.

DIPLONEIS CAMPYLODISCUS (GRUN.) CL.

Valve suborbicular; central nodule quadrate; horns divergent; costæ, 6 in

10 µ, alternating with double rows of alveoli; furrows broad, costate near

the horns.

Differs from Cleve's description in having 6, instead of 4, costæ in 10 µ.

Pensauken, N. J. (artesian well). Rare.

Pl. 20, Fig. 6.

MASTOGLOIA THWAITES (1856)

(mastos, a breast, and gloios, gelatinous, referring to the "mamillate

cushion" in which the frustules are often immersed)

Frustule rectangular. Valves similar, naviculoid. Central and axial areas

usually narrow or indistinct; striæ punctate, parallel in the middle. On

each side, between the valve and the zone, is a septate plate.

ANALYSIS OF SPECIES

Striæ interrupted by a hyaline furrow on each side of

the median line kinsmanii

Striæ not interrupted:

Loculi, five, or less exigua

more than five, equal, ending at distance from

the ends smithii

ending near the ends, distinct lanceolata

indistinct elegans

very numerous apiculata

unequal angulata

{87}Karsten states that there are two chromatophores, each of which extends

from the middle of one valve to the end and down the middle of the other

valve. Mereschkowsky says, however, that there are four plates or

chromatophores, sometimes on the valve, sometimes on the zone, according to

the species, and that two long pyrenoids unite the two opposite

chromatophores.

MASTOGLOIA KINSMANII LEWIS

Valve lanceolate-elliptical, with sub-rostrate ends; loculi more numerous

than in M. angulata but less than in M. apiculata, the middle ones larger.

Median line with a sulcus on each side; central area quadrate.

_Mastogloia braunii_ Grun. (According to Cleve).

Atlantic City.

Pl. 17, Fig. 16.

MASTOGLOIA EXIGUA LEWIS

Valve elliptical- or linear-lanceolate; loculi, 2-5, usually 3, larger in

the middle and rounded; central space small; striæ, 20-24 in 10 µ.

Along the coast.

Pl. 17, Fig. 24.

MASTOGLOIA SMITHII THWAITES

Valve lanceolate, sub-rostrate; loculi forming a wide band ending at a

distance from the ends; striæ transverse, with puncta forming longitudinal

rows; central area rounded or transversely elliptical.

Along the coast.

Pl. 17, Fig. 19.

MASTOGLOIA LANCEOLATA THWAITES

Valve lanceolate, with sub-rostrate apices; loculi very numerous; median

and central areas indistinct; striæ, 19 in 10 µ, punctate, convergent at

the ends.

Along the coast.

Pl. 17, Fig. 18.

MASTOGLOIA ELEGANS LEWIS

Valve lanceolate, acute; loculi indistinct or rudimentary, extending to the

ends; central area apparently quadrate, sometimes indistinct; puncta

distinct, 15 in 10 µ, in transverse and longitudinal rows.

Along the coast. Common.

Pl. 17, Fig. 20.

MASTOGLOIA APICULATA WM. SM.

Valve elliptical-lanceolate, sometimes with slightly produced apices;

median line between two ribs; central space very small; loculi numerous;

puncta in slightly radiating rows and in longitudinal lines.

Along the coast.

Pl. 17, Figs. 21, 22, 23.

MASTOGLOIA ANGULATA LEWIS

Valve elliptical, with produced apices; loculi usually less than 12,

unequal, the larger in the middle; striæ, 12 in 10 µ, puncta in decussating

rows. "Differs from apiculata in its more broadly elliptical shape, the

smaller number of its loculi and the angular character of its striation"

(Lewis).

{88}Considered by Cleve as synonymous with M. apiculata Grun., not Wm.

Smith, and by De Toni as synonymous with M. apiculata Wm. Sm. In any case,

M. angulata Lewis is not the same as M. apiculata Wm. Sm., the loculi of

which are equal.

Atlantic City. H. L. Smith T. S. No. 211.

Pl. 17, Fig. 17.

STAURONEIS EHR. (1843)

(stauros, a cross, and neis (naus), a boat)

Frustules free, sometimes geminate; valve as in Navicula but with a

stauros. Cell contents as in Navicula. Mereschkowsky, however, says that

the chromatophores always contain more pyrenoids than are found in

Navicula. Heinzerling gives the number as two to four in each

chromatophore.

Cleve includes under Naviculæ Microstigmaticæ all species of Stauroneis,

Pleurostauron, Schizostauron, certain Schizonemæ and Naviculæ. As a matter

of convenience, and because I have already included certain Schizonemæ and

Scoliopleura under Navicula, and because of the small number of species in

our locality, I have arranged them under the three divisions of Cleve as

follows:

_Stauroneis._--Forms having a true stauros, without diaphragms.

_Pleurostauron._--Forms like Stauroneis but with diaphragms at the ends.

_Schizostauron._--Forms having a bifid stauros.

STAURONEIS PHOENICENTERON EHR.

Valve lanceolate, obtuse; striæ radiate, 18 in 10 µ, distinctly punctate.

L. usually 125 µ but sometimes 200 µ.

Common in fresh water.

Pl. 27, Fig. 1.

STAURONEIS ANCEPS EHR.

Valve lanceolate, with rostrate or capitate ends; stauros in some cases

does not reach the margin. The varieties are very numerous.

_Var. gracilis (Ehr.) Cl._--Valve lanceolate, striæ very fine; margin of

stauros striated. L. 100 µ. Cape May, N. J. Pl. 27, Fig. 5.

_Var. amphicephala (Kuetz.) Cl._--Valve capitate at the ends; striæ, 24 in

10 µ. L. 47 µ. Fresh water. Pl. 27, Fig. 7.

_Var. ?_--Valve with produced ends; striæ, 30 or more in 10 µ. L. 104 µ.

Willistown, Pa. Pl. 27, Fig. 4.

_Var. ?_--Valve with produced ends; striæ, about 28 in 10 µ, punctate. L.

47 µ. Newtown Square. Pl. 27, Fig. 8.

_Var. ?_--Valve with produced ends; striæ, 22 in 10 µ, showing a tendency

to form longitudinal rows of puncta as in Stauroneis stodderi Greenleaf,

but the rows are not so evident. L. 60 µ. Pavonia, N. J., artesian well.

Pl. 27, Fig. 9.

STAURONEIS FRICKEI VAR. ANGUSTA N. VAR.

Valve lanceolate, gradually tapering to the obtuse ends; terminal fissures

prominent, forking at a distance of 7 µ from the ends. Frustules frequently

geminate. L. 173 µ.

Newtown Square. Rare.

Pl. 26, Fig. 18.

Near Stauroneis frickei A. S. (Atlas, Pl. 242, Fig. 16), except that the

stauros is narrow at the margin.

{89}STAURONEIS SALINA WM. SM.

Valve lanceolate, obtuse; stauros narrow, with short, scattered striæ at

the margin, 18 in 10 µ, punctate. L. 65 µ.

Along the coast. Common.

Pl. 27, Fig. 6.

STAURONEIS LEGUMEN EHR.

Valve elliptical-lanceolate, inflated in the middle, with produced

sub-capitate or rostrate ends separated by diaphragms. Stauros wide,

striated at the margins; axial area very narrow; striæ radiate, about 26

(?) in 10 µ, punctate. L. 28 µ.

Pavonia, N. J., artesian well.

Pl. 39, Fig. 15.

In Cleve's description and Van Heurck's figure, the median inflation is

"not larger than the others." In the present form the median inflation is

wider.

STAURONEIS ACUTA WM. SM.

Valve rhombic-lanceolate, obtuse; a diaphragm at each end; stauros widened

outwards; striæ, 15 or 16 in 10 µ, punctate. L. 130 µ.

Blue clay.

Pl. 27, Fig. 2.

STAURONEIS AMERICANA A. S.

Valve elliptical-lanceolate, obtuse; striæ, 14 in 10 µ. L. 119 µ.

Pavonia, N. J., artesian well. Rare.

The only specimen found is asymmetrical with respect to the transverse

axis.

On Plate 40, Fig. 4, is illustrated an abnormal form of Stauroneis,

apparently near S. acuta, having an elongated central nodule and radiating,

curved and coarsely punctate striæ. Blue clay.

STAURONEIS SMITHII GRUN.

Valve lanceolate, inflated in the middle and at the ends, which have

diaphragms and are produced into rostrate apices; stauros reaching the

margin; striæ parallel, about 25 in 10 µ (28 to 30, Cleve), distinctly

punctate.

Not uncommon in meadow pools near Newtown Square.

Pl. 27, Fig. 11.

STAURONEIS CRUCICULA (GRUN.) CL.

Valve lanceolate, with obtuse, produced ends; stauros bifid; striæ, 24 in

10 µ, oblique, parallel to the branches of the stauros, closer at the ends,

punctate. L. 32 µ.

Newtown Square. East Park Reservoir. Rare.

Pl. 27, Fig. 10.

NAVICULA BORY (1826)

(dim. of navis, a boat)

Valve linear to elliptical; ends acute, rounded, rostrate, capitate or

truncate; axial area usually distinct; central area distinct, rounded or

rarely extended into a transverse fascia; striæ transverse or radiate,

punctate; central area not dilated into a transverse stauros nor into

horns.

{90}The endochrome in the greater number of species consists of two

chromatophores extending along the zone and sometimes partly over the

valves. Sometimes, however, as in N. hennedyi, N. lyra and N. humerosa, the

bands are on the valves. Certain species have four bands, others eight, and

in one the endochrome is granular. (Mereschkowsky, l. c., p. 9 et seq.)

Pyrenoids are usually absent. On account of the diversity of the

chromatophores, Mereschkowsky considers the genus not homogeneous. The

difficulty of arranging groups according to the cell contents, however, is

so great that, for the present, the species must be described by the usual

characteristics of the valves and divided as follows, according to Cleve,

to the extent of employing the classification of all Naviculoid forms as

applicable, especially to the species of Navicula. Van Heurck's analysis

includes Pinnularia, Trachyneis, Diploneis, Caloneis, Neidium and

Anomoeoneis, which are here separated, while N. lyra and N. hennedyi are

placed in different groups, although they are closely related. In other

respects Cleve's divisions correspond, to some extent, to those of Van

Heurck.

The genus Navicula at one time included the following: Dictyoneis,

Pleurosigma, Gyrosigma, Caloneis, Neidium, Diploneis, Frustulia,

Trachyneis, Anomoeoneis, Pinnularia and Stauroneis, and few forms with a

raphe escaped. For this reason the diagnosis of the present genus is

somewhat limited. Pleurosigma and Gyrosigma differ from Navicula in their

outline, Dictyoneis in the double stratification, Caloneis in the marginal

lines, Neidium in the median and terminal fissures, Diploneis in the horns,

Frustulia in the terminal nodules, Trachyneis in the stratification of the

valve, Anomoeoneis in the longitudinal arrangement of the puncta,

Pinnularia in the smooth costæ and Stauroneis in the stauros.

As the object of the present work is to aid the student of local forms in

the identification of species by the briefest methods, the further

discussion of the reasons for classification will be left for his

gratification in referring to the authorities on the subject.

PUNCTATÆ CLEVE

Valve elliptical to lanceolate; central nodule not stauroid or continued

into lyriform spaces; striæ distinctly or coarsely punctate, in radiate

rows.

NAVICULA MACULATA (BAIL.) CL.

Valve lanceolate-elliptical, with produced or sub-rostrate ends; axial area

narrow, wider near the ends and dilated to a rounded, transverse central

area; striæ radiate, 6 in 10 µ, puncta, 7 in 10 µ, in irregular,

longitudinal rows. L. 90 to 120 µ (Cl.).

_Stauroneis maculata_ Bail.

_Navicula fischeri_ A. S.

Blue clay. Along the coast, especially southward.

Pl. 24, Fig. 1.

NAVICULA LATISSIMA GREG.

Valve oblong-elliptical or elliptical-lanceolate, with sub-cuneate ends;

axial area lanceolate, widened in the middle to an orbicular space; striæ

radiate, 7 in 10 µ, puncta, 11 in 10 µ, the median striæ alternating with

short striæ along the sides. L. 50-150 µ (Cl).

Blue clay. Pavonia, N. J., artesian well.

Pl. 24, Fig. 3.

{91}NAVICULA LATISSIMA VAR. ELONGATA (PANT.) CL.

Valve elliptical-lanceolate, with rounded ends; striæ and puncta closer

than in the type form; axial area narrow, widened in the middle; terminal

fissures hook-shaped, turned in different directions.

_Navicula humerosa_ var. _elongata_ Pant.

Fossil at Buckshutem, N. J.

Pl. 24, Fig. 5.

NAVICULA FUCHSII PANT.

Valve elliptical, with slightly produced apices; axial area wide,

lanceolate; central area orbicular; striæ alternately longer and shorter in

the middle, 10-12 in 10 µ; puncta on the border of the axial area larger,

elongated; median fissures incrassate.

_Navicula humerosa_ var. _fuchsii_ (Pant.) Cl.

_Navicula_ (_latissima_ var.?) _fuchsii_ Pant.

Port Penn, Delaware River.

Pl. 24, Fig. 6.

NAVICULA HUMEROSA BRÉB.

Valve lanceolate-elliptical or oblong-elliptical, with sub-cuneate or

sub-rostrate ends; axial area narrow, lanceolate; central area rounded,

somewhat transverse; terminal fissures hook-shaped, in the same direction;

central pores incrassate; striæ, 11 in 10 µ, the middle alternately longer

and shorter, closer at the ends. L. 60-86 µ. Variable in size, outline and

fineness of striation.

N. monilifera Cleve (N. granulata Bréb.) differs in having coarser striæ.

Blue clay. Along the coast.

Pl. 25, Fig. 5.

NAVICULA PUSILLA WM. SM.

Valve ovate-elliptical, with rostrate or sub-rostrate ends; axial area

narrow; central area elliptical; striæ radiate, 10-12 in 10 µ in the middle

where they are longer and shorter alternately, closer at the ends; median

fissures somewhat incrassate, terminal in the same direction. L. 47 µ.

Smith's Island, Delaware River.

Pl. 25, Figs. 4, 6?

Cleve gives the striæ as 13-18 in the typical form, and 11-13 in varieties.

In the form here figured the striation is as stated by De Toni, but is

about 19 at the ends.

Fig. 6 appears to be a small form of N. pusilla, near lanceolata Grun., at

least according to the figure in "Arctic Diatoms," but not Gregory's

figure. It occurs rarely in fresh water at Newtown Square. It may be a

small form of N. punctulata and, if so, is probably accidental, as the

material is entirely fresh-water.

NAVICULA PUSILLA VAR. SUBCAPITATA N. VAR.

Valve elliptical with rostrate-capitate and truncate ends; striæ about 12

in 10 µ in the middle where they are unequal; axial area narrow, slightly

widened in the middle; central pores incrassate, terminal fissures in the

same direction. Differs from type in outline and centre.

Pavonia, N. J., artesian well. Rare.

Pl. 25, Fig. 8.

{92}NAVICULA DELAWARENSIS GRUN.

Valve elliptical-lanceolate, with sub-rostrate ends; axial area narrow,

lanceolate, widened in the middle; striæ about 10 in 10 µ; in the middle,

much closer at the ends; puncta in the middle, 9 in 10 µ, closer and much

smaller at the ends. L. 58-95 µ.

Cleve (Le Diatomiste, Vol. 2, p. 14) states that this form is very near N.

pusilla but is much larger. Specimens from Smith's Island measure 58-65 µ,

from Wildwood, 95 µ in length.

Pl. 25, Fig. 3.

NAVICULA PUNCTULATA WM. SM.

Valve elliptical-lanceolate, with sub-rostrate ends; axial area narrow,

central area rounded; striæ, 11 in 10 µ, closer at the ends, a few shorter

in the middle; puncta, 10 in 10 µ. L. 54 µ.

_Navicula marina_ Ralfs.

Port Penn, Delaware River (brackish water).

Pl. 25, Fig. 9.

"Although this species is described as marine in the Synopsis of Prof.

Smith, I have never found it in purely marine localities" (Donkin).

NAVICULA PUNCTATA VAR. ASYMMETRICA LAGERSTEDT

Valve lanceolate, with rostrate ends; axial area narrow, central area

transverse, irregular; striæ radiate, punctate, 12 in 10 µ. L. 36 µ.

_Navicula amphibola_ Cleve.

Blue clay.

Pl. 27, Fig. 15.

NAVICULA BRASILIENSIS VAR. BICUNEATA CL., FORMA CONSTRICTA

Valve oblong-elliptical, slightly constricted, with cuneate-rostrate ends;

axial area narrow; central area dilated transversely and unilaterally;

striæ, 9 in 10 µ; puncta closer at the border and in irregular longitudinal

rows in the middle; terminal fissures small, hook-shaped, turned in the

same direction. L. 93 µ.

Corresponds closely to Cleve's variety except in the constriction.

Blue clay.

Pl. 25, Fig. 2.

NAVICULA LACUSTRIS GREG.

Valve lanceolate, sub-acute; axial area narrow; central area orbicular;

striæ radiate, 14 in 10 µ, punctate, the median puncta sometimes more

distant than the others.

Blue clay. Rare.

Pl. 27, Fig. 12.

LYRATÆ CL.

Valve elliptical or elliptical-lanceolate; striæ punctate, transverse;

axial area narrow or indistinct; central area expanded on each side into

lyre-shaped or horn-like blank spaces.

NAVICULA PRÆTEXTA EHR.

Valve elliptical; lateral areas not regular, with scattered puncta; striæ

radiate, 5 or 6 in 10 µ; puncta, 7 or 8 in 10 µ; along the axial area, a

single or double row of puncta; at {93}the middle of the border, on each

side, two striæ approach each other closely with a short stria between

them; terminal fissures small, in the same direction. L. 120 µ.

Port Penn, Delaware River.

Pl. 24, Fig. 2.

While variable in size and striation, approaching N. hennedyi, this

species, as here figured, is found in the Miocene and later deposits and is

extant in most parts of the world.

NAVICULA IRRORATA GREV.

Valve oblong-elliptical, with cuneate-rostrate ends; striæ, 7 or 8 in 10 µ,

puncta, 7 in 10 µ; axial area bordered by puncta in unequal, transverse

rows. L. 84 µ.

Blue clay. Rare.

Pl. 24, Fig. 4.

NAVICULA HENNEDYI WM. SM.

Valve elliptical; areas semilanceolate; striæ about 11 in 10 µ, sometimes

longer and shorter on the margin; short rows of transverse striæ along the

axial area.

Blue clay.

Pl. 25, Fig. 12.

_Var. circumsecta Grun._--As in the type but with the lateral areas faintly

striate or punctate.

_Var. manca A. S._--Valve lanceolate-elliptical, the lateral areas narrow

and convergent toward the ends; short rows of transverse striæ along the

axial area; striæ, 9 in 10 µ; central pores incrassate.

Blue clay.

Pl. 25, Fig. 11.

NAVICULA LYRA EHR.

Valve elliptical, with rounded, sub-rostrate or sub-cuneate ends; lateral

areas narrow; striæ, 6 to 14 in 10 µ (Cl.), punctate. L. 50-180 µ.

_Var. ehrenbergii Cl._--Lateral areas constricted in the middle, divergent

at the ends. Cleve refers to Schmidt, Atlas, Pl. 2, Fig. 25, which is not

divergent at the ends.

Along the coast.

Pl. 25, Fig. 10.

A narrower form occurs which has the areas divergent.

_Var. ?_--Valve elliptical, lateral areas narrow, convergent at the ends

with short rows of punctate striæ; marginal striæ, 10 in 10 µ, punctate. L.

60 µ.

Squan River, N. J.

Pl. 20, Fig. 5.

_Var. dilatata A. S._--Valve elliptical, rostrate; lateral areas convergent

in the middle and nearly parallel or convergent at the ends.

Blue clay.

Pl. 25, Fig. 13.

N. lyra is exceedingly variable in outline, fineness of striation and in

the lateral areas. Intermediate forms occur approaching N. hennedyi and N.

spectabilis. In N. hennedyi the lateral areas are broad, semilanceolate,

not narrowed in the middle. In N. spectabilis the lateral areas are broad

and narrowed in the middle. In N. lyra the lateral areas are narrow and

either constricted or not in the middle. In many forms in {94}these three

species the lateral areas are more or less striated or punctate. Cleve does

not consider this a distinction of any importance, although certain

varieties are founded upon it. All three species are very common in the

blue clay and along the coast, but their varieties are too numerous to

describe or figure.

NAVICULA SPECTABILIS VAR. EMARGINATA CL.

Valve elliptical; lateral areas broad, narrowed in the middle, delicately

striated; marginal striæ, 10 in 10 µ. L. 70 µ.

Blue clay.

Pl. 25, Fig. 7.

NAVICULA PYGMÆA KUETZ.

Valve elliptical, appearing hyaline; axial and central areas faint; lateral

areas convergent in the middle; striæ indistinct, about 25 in 10 µ. L. 23

µ.

Brandywine Creek (Palmer).

Pl. 27, Fig. 23.

DECUSSATÆ CL.

Valve elliptical or lanceolate; axial area narrow; central area small;

striæ punctate, in transverse and oblique, curved rows.

NAVICULA PLACENTA EHR.

Valve elliptical, with short, rostrate-capitate ends; axial area narrow;

central area elliptical; striæ in two directions, the transverse about 22

(to 27, Cl.) in 10 µ, the oblique striæ crossing in both directions in

curved lines appearing "coarser than the transverse" (Lewis).

A very peculiar species which, as Cleve remarks, seems not to be allied to

any other. L. about 35 µ, quite constant in size. It is reported from

Finland, Scotland, Hungary and New Zealand. Dr. Lewis found it in the

Delaware River. It is occasional in the Schuylkill River and the blue clay,

and very abundant on Marchantia and mosses on the wet rocks of the upper

Wissahickon (F. J. Keeley).

Pl. 27, Fig. 17.

LINEOLATÆ CL.

Valve more or less lanceolate; axial area narrow or indistinct; striæ

radiate or parallel, lineate, that is, with the puncta closer than the

striæ.

NAVICULA RADIOSA KUETZ.

Valve lanceolate with sub-rostrate apices; axial area indistinct; central

area small; striæ radiate in the middle, from 6 to 8 in 10 µ, and

convergent at the ends, about 12 in 10 µ. L. 47 µ.

Very common in fresh water.

Pl. 26, Fig. 17; Pl. 40, Fig. 9.

NAVICULA PEREGRINA EHR.

Valve lanceolate, obtuse; axial area narrow; central area large, rounded or

slightly irregular; striæ coarse in the middle, 5 in 10 µ, radiate;

convergent at the ends, 7 or 8 in 10 µ.

Abundant in brackish water. Delaware River.

Pl. 26, Fig. 20.

{95}NAVICULA CYPRINUS (WM. SM.)

Valve lanceolate, slightly gibbous in the middle, sub-cuneate at the ends;

axial area narrow; central area small; striæ radiate in the middle, 10 in

10 µ, with shorter, transverse striæ intermediate; transverse at the

extreme ends. L. 82 µ.

_Navicula digito-radiata_ var. _cyprinus_ (Ehr. ?) Wm. Sm. Whether the form

here figured is Ehrenberg's or not, it is the species known as Pinnularia

cyprinus Ehr. of Wm. Smith.

Common in Shark River, N. J.

Pl. 26, Fig. 21.

NAVICULA REINHARDTII GRUN.

Valve elliptical or elliptical-lanceolate, with broad, rounded ends; axial

area narrow, widened at the ends to the width of the valve; central area

widened transversely to an irregular, quadrate space; striæ coarse, 8 in 10

µ, distinctly lineate, alternately longer and shorter in the middle,

radiate, nearly transverse at the ends. L. 59 µ.

Blue clay. Rare.

Pl. 26, Fig. 22.

NAVICULA LANCEOLATA VAR. ARENARIA (DONK.) CL.

Valve lanceolate; axial area very narrow or indistinct; central area small,

rounded; striæ radiate, 11 in 10 µ in the middle, closer at the ends. L.

47-54 µ.

_Navicula arenaria_ Donk.

Shark River, N. J.

Pl. 26, Fig. 23.

NAVICULA SALINARUM GRUN.

Valve elliptical-lanceolate with produced sub-capitate or rostrate ends;

striæ radiate in the middle, longer and shorter; transverse at the ends,

lineate. L. 32 µ.

Atlantic City, N. J.

Pl. 26, Fig. 24.

NAVICULA VIRIDULA VAR. ROSTELLATA KUETZ.

Valve lanceolate with rostrate ends; axial area very narrow, central area

orbicular; striæ radiate in the middle, about 12 in 10 µ, convergent at the

ends and closer. L. 43 µ.

Common in fresh water.

Pl. 26, Fig. 16.

NAVICULA GRACILIS VAR. SCHIZONEMOIDES (EHR.) V. H.

Valve lanceolate, obtuse; axial area widened in the middle; striæ radiate

in the middle, about 12 in 10 µ, transverse or slightly convergent at the

ends. L. 45-60 µ. Occurs in gelatinous tubes; usually found free.

_Colletonema neglectum_ Thwaites.

Fresh water.

Pl. 26, Fig. 19.

NAVICULA RAMOSISSIMA (AG.) CL.

Valve lanceolate, sub-acute; axial area very narrow; central area scarcely

widened; striæ, 12 in 10 µ, parallel throughout. L. 45 µ.

_Micromega ramosissimum_ Ag.

_Schizonema smithii_ Kuetz. (not Ag.).

East River, N. Y.

Pl. 26, Fig. 14.

{96}NAVICULA ANGLICA RALFS

Valve elliptical, with sub-capitate or rostrate ends; axial area narrow,

central area small; striæ radiate, 12-13 in 10 µ, distinctly punctate. L.

26 µ.

Fresh water.

Pl. 26, Fig. 26.

NAVICULA GASTRUM EHR.

Valve elliptical, with rostrate ends; axial area narrow, central area

transverse or irregular; striæ radiate, 9 in 10 µ in the middle. L. 26 µ.

The form here figured approaches N. anglica.

Kirkwood Pond, N. J.

Pl. 26, Fig. 25.

NAVICULA DICEPHALA WM. SM.

Valve linear, with rostrate or rostrate-capitate ends; axial area narrow,

central area rectangular, transverse; striæ radiate, 12 in 10 µ. L. 32 µ.

Fresh water.

Pl. 27, Fig. 16.

NAVICULA HUMILIS DONK.

Valve elliptical, with broad, rostrate ends; axial area narrow; central

area small; striæ radiate and distant in the middle, convergent at the

ends, coarse, appearing costate, averaging 9 in 10 µ. L. 19 µ. As Donkin

states, the striæ are "very conspicuous."

_Navicula hungarica_ var. _capitata_ (Ehr.) Cl.

_Navicula globiceps_ Lagerstedt, according to Cleve.

Willistown, Pa.

Pl. 27, Fig. 24.

NAVICULA PINNATA PANT. ?

Valve lanceolate, obtuse; axial area narrow, widened in the middle; striæ

coarse, 7 in 10 µ in the middle, radiate, 10 in 10 µ at the ends and

transverse, indistinctly lineate. L. 40 µ.

Near _Navicula ardua_ Mann (Diat. Albatross Voy., Cont. U. S. Nat.

Herbarium Vol. 10, Part 5, p. 336, Pl. 53, Fig. 2) which, however, is said

to have "strictly unbeaded costæ."

Pavonia, N. J., artesian well.

Pl. 27, Fig. 20.

NAVICULA PENNATA A. S.

Valve lanceolate, acute; axial area narrow; central area quadrate,

transverse; striæ radiate, coarse, 5 in 10 µ, lineate. L. 68-95 µ (Cleve).

Pavonia, N. J., artesian well.

Pl. 27, Fig. 22.

NAVICULA INFLEXA GREG.

Valve slightly elliptical-lanceolate, sub-acute, smooth at the ends; axial

area narrow, widened in the middle; striæ radiate, 11 in 10 µ, lineate.

Frustule in zone view constricted in the middle. L. 28-45 µ.

Common along the coast.

Pl. 27, Figs. 18 and 19.

{97}NAVICULA OBLONGA KUETZ.

Valve linear-lanceolate, with broad, rounded ends; margin sometimes

undulate; axial area narrow; central area large, orbicular; striæ in the

middle distant, radiate, convergent at the ends and curved or sharply bent,

7 in 10 µ, lineate. L. 70-200 µ (Cleve).

Blue clay. Occasional in fresh water.

Pl. 27, Fig. 21.

NAVICULA HASTA PANT.

Valve lanceolate, gently tapering to the obtuse, produced ends; axial area

lanceolate, widened to an orbicular space in the middle; striæ radiate, the

median coarse and quite distant, 5 in 10 µ, becoming closer at the ends

where they are 12 in 10 µ, lineate. The distance between the median striæ

gives the appearance of a stauros.

Occasional in the blue clay.

Pl. 27, Fig. 13.

NAVICULA HASTA VAR. PUNCTATA N. VAR.

Valve as in type but with striæ in the middle distinctly punctate and

reaching the median line.

Greenwich Point, Philadelphia.

Pl. 27, Fig. 14.

NAVICULA RHYNCOCEPHALA KUETZ.

Valve lanceolate, with produced ends; axial area indistinct; central area

small, rounded; striæ radiate in the middle, convergent at the ends, 10-11

in 10 µ, punctate. L. 42 µ.

Fresh water. Common.

Pl. 31, Fig. 8.

NAVICULA CRYPTOCEPHALA KUETZ.

Valve lanceolate, with rostrate ends; axial area indistinct; central area

small; striæ, 16 in 10 µ, lineate, radiate in the middle, convergent at the

ends. L. 28 µ.

Common in fresh water.

Intermediate forms occur between N. rhyncocephala and N. cryptocephala.

Pl. 31, Fig. 9.

NAVICULA LONGA (GREG.) RALFS

Valve slender, rhombic, elongated, with acute ends; axial area indistinct;

central area small; striæ, 6 or 7 in 10 µ, radiate in the middle, elsewhere

transverse; central pores closely approximate. L. 120 µ.

New Rochelle, N. Y.

Pl. 31, Fig. 10.

Cleve refers this form to N. directa var. remota Grun. Some specimens are

found in this locality showing the "generally twisted" median line

mentioned by Gregory.

MESOLEIÆ CL.

Valve linear or elliptical; axial area narrow; central area quadrate; striæ

radiate, finely punctate.

NAVICULA MUTICA KUETZ.

Valve ovate, elliptical or lanceolate; axial area narrow; central area

dilated into a stauros not reaching the margin; striæ about 20 in 10 µ,

more distant in the middle, radiate, punctate. A punctum occurs on one side

of the central nodule.

{98}Reported from New Jersey in fresh water. I have not found it. The

figure is from a specimen from another locality.

Pl. 26, Fig. 6.

NAVICULA MINIMA GRUN.

Valve broadly elliptical, 13-15 µ in length; axial area narrow; central

area small but with a quadrate pseudo-stauros which is striated; striæ,

about 28 in 10 µ, radiate.

Agrees closely with N. saugeri var. Grun. in V. H. Synopsis, Pl. 14, Fig.

16, said to be intermediate between N. minima and N. atomoides Grun. N.

minima var. atomoides Grun. is smaller.

Common in water-troughs.

Pl. 26, Fig. 13.

NAVICULA PUPULA VAR. BACILLARIOIDES GRUN.

Valve linear, with rounded ends; axial area linear, expanding on both sides

near the ends of the valve, forming a transverse lunate space; central area

small, apparently expanded into a stauros, which, however, is striated;

striæ, 18 in 10 µ, at the middle, closer at the ends, punctate. L. 54 µ.

Pavonia, N. J., artesian well.

Pl. 26, Fig. 9.

BACILLARES CL.

Valve linear or linear-elliptical, with broad ends; axial area narrow, the

median line enclosed in siliceous ribs; striæ finely punctate, more distant

in the middle.

NAVICULA BACILLUM EHR.

Valve linear, with rounded ends; axial area enclosed in siliceous ribs and

slightly expanded on each side at the ends; terminal nodules incrassate;

central area small, elliptical; striæ, 15 in 10 µ in the middle,

transverse, distinctly punctate, closer at the ends L. 47 µ.

Fresh water.

Pl. 26, Fig. 10.

Cleve describes the form as having slightly radiate striæ in the middle.

There is considerable difference in the descriptions of Cleve, Donkin,

Grunow and Van Heurck, as also in all of the figures.

NAVICULA AMERICANA EHR.

Valve oblong-linear, with rounded ends, sometimes slightly constricted;

axial area about one-half the width of the valve, dilated in the middle;

striæ parallel in the middle, radiate at the ends, 15-16 in 10 µ. A punctum

is usually found in the central nodule. L. 55-154 µ.

Blue clay. Occasional in fresh water.

Pl. 26, Fig. 8.

DECIPIENTES CL.

Valve lanceolate, with obtuse ends; axial area narrow; central area

orbicular; striæ radiate in the middle and more distant.

NAVICULA SEMEN EHR.

Valve elliptic-lanceolate, with sub-rostrate, truncate apices; axial area

narrow, {99}sinuous; central area orbicular; terminal fissures small,

hook-shaped; striæ robust, 7 or 8 in the middle, closer at the ends,

indistinctly punctate or lineolate.

Blue clay. Not common.

Pl. 26, Fig. 11.

Cleve states that this form belongs to the post-glacial deposits and is

found living only in the Hartz Mountains.

NAVICULA INTEGRA WM. SM.

Valve lanceolate with triundulate margins and rostrate-apiculate ends;

striæ radiate, more distant in the middle, 20-23 in µ, punctate; axial area

very narrow, central area rounded or elliptical. L. 33-43 µ.

Pavonia, N. J., artesian well. Common in Chester River, Md.

Pl. 26, Fig. 5.

MICROSTIGMATICÆ CL.

Valve lanceolate; axial area narrow; central area small, rounded; striæ

finely punctate, nearly parallel. (Includes here only the division

Libellus.)

NAVICULA TUMIDA (BRÉB.) CL.

Valve lanceolate, with rounded ends; axial area narrow, central area

elliptical; raphe slightly sigmoid; striæ, 13 in 10 µ, finely punctate, a

few shorter in the middle.

_Scoliopleura tumida_ (Bréb.) V. H.

Cape May, N. J.

Pl. 25, Fig. 1.

NAVICULA GREVILLEI (AG.) CL.

Frustules in gelatinous tubes, rectangular; zone with numerous longitudinal

divisions. Valve elliptical-lanceolate, obtuse; axial area narrow, central

area small; striæ lineate, about 18 in 10 µ in the middle where they are

slightly radiate and more evident, closer near the ends and transverse;

median line with terminal pores distant from the ends. L. 60 µ.

_Schizonema grevillei_ Ag.

East River, N. Y.

Pl. 31, Figs. 3 and 4.

NAVICULA LIBELLUS GREG.

Valve rhombic-elliptical, obtuse at the ends; axial area narrow, central

rounded, small; striæ punctate, slightly radiate, about 19 in 10 µ;

terminal fissures close to the ends, indistinct. L. 60 µ.

Cleve describes this form as having acute ends, while Gregory states that

it is "more obtuse and broader than N. rhombica." Gregory's Figure 101

apparently shows the ends acute, but he says that the valve view is

"rhombic or elliptic-lanceolate, broad, with obtuse ends" (Diat. of the

Clyde, p. 57, Pl. 6).

Hackensack Swamp, N. J.

Pl. 31, Fig. 5.

ORTHOSTICHÆ CL.

Valve lanceolate or elongated; axial area narrow; central area sometimes

apparently dilated into a stauros; striæ punctate, the puncta in transverse

and longitudinal rows.

{100}NAVICULA CUSPIDATA KUETZ.

Valve rhombic-lanceolate, with acute ends; axial area linear, narrow, not

widened in the middle; striæ transverse, 14-19 in 10 µ (Cl.). L. 70-150 µ.

Blue clay. Not uncommon in fresh water.

Pl. 26, Figs. 1 and 2.

Fig. 2 represents an inner valve or stratum, with strong costæ variable in

size, formerly known as Surirella craticula Ehr.

_N. cuspidata var. ambigua (Ehr.) Cl._--Valve elliptical-lanceolate, with

rostrate ends, smaller than the type and with finer striæ.

Crum Creek.

Pl. 26, Fig. 3.

NAVICULA SPICULA (HICKIE) CL.

Valve narrow, lanceolate with acute ends; axial area narrow, central area

dilated into a stauros reaching the margin; transverse striæ, 25-29 in 10

µ, longitudinal closer. L. 50-130 (Cl.).

Sometimes confused with N. crucigera.

_Stauroneis spicula_ Hickie.

Newark, N. J.

Pl. 26, Fig. 4.

NAVICULA CRUCIGERA (WM. SM.) CL.

Valve lanceolate, narrow, with acute apices; central nodule a stauros

reaching the margin but crossed by two or three coarser striæ; transverse

striæ, 12 in 10 µ, punctate, the puncta about 25 in 10 µ. L. 80-100 µ

(Cl.). Frustules in gelatinous tubes or free.

_Schizonema cruciger_ Wm. Sm.

Pl. 26, Fig. 15.

Reported as occurring in New York Bay, but I have not seen it. The figure

is from a specimen from another locality.

MINUSCULÆ CL.

Valve lanceolate or elliptical, chiefly distinguished by the small size;

axial area indistinct; central area small; striæ radiate, very finely

punctate.

NAVICULA ATOMUS NÆGELI

Valve elliptical, 6-8 µ in length; striæ radiate, 26-30 µ, closer near the

ends; axial area linear, scarcely widened in the middle.

Water-troughs and ditches. Probably common, but frequently not noticed

because of its minuteness. A mounting medium of the highest refractive

index, such as realgar, is required to resolve the striæ. In the figure the

striæ are drawn a little coarser than they appear in most specimens.

Pl. 26, Fig. 12.

LÆVISTRIATÆ CL.

Valve lanceolate, axial area distinct; central area orbicular; striæ

coarse, indistinctly punctate, approaching the costæ of Pinnularia.

{101}NAVICULA YARRENSIS GRUN.

Valve elliptical-lanceolate, with rounded ends; axial area lanceolate,

widened in the middle; striæ, 5 in 10 µ. L. 97 µ.

Cape May, N. J. Common.

Pl. 25, Fig. 14.

Fig. 15, a smaller form, 65 µ in length; striæ, 6 in 10 µ.

Fig. 16, 54 µ in length; striæ, 8 in 10 µ (near var. valida Pant.).

NAVICULA ELEGANS WM. SM.

Valve elliptical-lanceolate, with produced ends; axial area very narrow,

central area large, orbicular; striæ strongly divergent in the middle,

slightly, if at all, convergent at the ends, curved toward the margin,

indistinctly lineate, 9 in 10 µ. L. 95 µ.

Blue clay. Not rare.

Pl. 31, Fig. 1.

_Navicula elegans var. cuspidata Cl._--Valve as in type form but smaller

and with rostrate apices; striæ, 10 in 10 µ. L. 82 µ.

Belmar, N. J.

Pl. 31, Fig. 2.

Cleve remarks that the type form is acute and the striæ 9, while the var.

cuspidata has 12 striæ in 10 µ. In Fig. 1, Pl. 31, is represented a valve

having 9 striæ in 10 µ, but not acute, while Fig. 2, with but slight

variation in striæ, is more cuspidate. It is probable there are

intermediate variations.

NAVICULA PALPEBRALIS BRÉB.

Valve elliptical-lanceolate, with acute apiculate ends; axial area broad,

lanceolate; striæ radiate, lineate, about 11 in 10 µ. L. 60 µ.

Along the coast.

Pl. 31, Figs. 6 and 7.

On Plate 40, Fig. 5, is represented an abnormal form of Navicula in which

the central pores are in a line transverse to the longitudinal axis and

each raphe is curved in a line which almost returns to the centre. The

puncta are in curved lines radiating from the rounded hyaline centre.

Pavonia, N. J., artesian well.

Weissflog has described valves of Navicula somewhat similar in punctation.

PINNULARIA EHR. (1843)

(pinnula, a small feather)

Valve linear or nearly so, with rounded ends; axial area broad; central and

terminal areas large; costæ smooth, transverse or radiating, usually

convergent at the ends.

The costæ are channels on the inside of the valve, closed, except in the

middle where elliptical foramina, opening into the interior of the valve,

give rise through their terminal margins to the two longitudinal lines on

each side of the valve. The raphe begins as a groove in the side of the

conical central nodule and continues as a cleft at right angles to the

plane of the surface of the valve, in which case the raphe forms a single

line; if the raphe is inclined to the valve surface, then two lines appear

in projection, the upper and lower edges of the cleft. In some forms the

surface of the edge of the raphe on one side is folded or grooved for a

considerable distance, and the opposite edge is elevated into a ridge or

{102}tongue fitting into the groove. In such cases it is possible, in

projection, to see the upper or outer edges of the raphe, the lower edges

and the edges of the tongue and groove, thus showing four lines; sometimes,

when the tongue and groove do not meet, six lines. The so-called inner

channel is the part of the raphe on the inside of the tongue, and the

so-called exterior channel is the part of the raphe on the outside of the

tongue. If, in addition to this formation of the raphe, the plane of

cleavage changes toward the terminal nodules, the lines will cross each

other and, when two are superimposed, disappear altogether. For the careful

examination of the raphe it is necessary to employ large forms, and it is

advisable to use nitrate of silver which remains in the raphe, and, as in

slides mounted by Mr. F. J. Keeley, shows in a beautiful manner the entire

outline of raphe and fissures. The terminal fissures owe their separation

to the different directions taken by the two edges of the raphe on each

side, one edge bending in a wide curve toward the end of the valve, showing

two lines, the upper and lower edges of one side of the raphe when inclined

to the plane of the surface, and the other edge of the raphe turning

suddenly in an opposite direction and ending abruptly in a curve, giving

rise to the appearance, by diffraction, of a punctum.

Pl. 40, Figs. 13, 14 and 15.

Endochrome consists of two chromatophores lying on the zones.

Pinnularia is usually divided into the Majores, or larger, and the Minores,

or smaller forms, the latter being further divided according to their

striæ. The following classification is chiefly that of Cleve.

_Majores._--Valve large, linear with parallel or slightly radiate striæ and

broad axial area.

_Gracillimæ._--Valve small, striæ parallel or nearly so; axial area very

narrow.

_Capitatæ._--Valve with capitate or rostrate ends; striæ radiate.

_Divergentes._--Striæ strongly radiate.

_Brevistriatæ._--Striæ short.

_Distantes._--Striæ distant.

_Tabellariæ._--Striæ radiate in the middle, strongly convergent at the

ends.

_Marinæ._--Marine forms.

MAJORES

PINNULARIA MAJOR (KUETZ.) WM. SM.

Valve linear, usually slightly gibbous in the middle and at the ends; raphe

oblique; axial area less than one-third the width of valve, convergent at

the ends; striæ, 7 or 8 in 10 µ, radiate in the middle, convergent at the

ends, crossed by a narrow band. L. ? to 300 µ.

Blue clay. Fresh water. Abundant at Middletown, Delaware Co. (T. C.

Palmer).

Pl. 28, Fig. 4.

Fig. 9, Pl. 29, is one of a number of smaller forms which are difficult to

determine, approaching P. viridis.

PINNULARIA MAJOR VAR. PULCHELLA N. VAR.

Valve strongly gibbous in the middle and gradually widened to the rounded

ends; axial area broad, less than one-third the width of the valve, widened

unilaterally in the middle; striæ, 7 in 10 µ, crossed by a band nearly as

wide as the length of the costæ and scarcely distinct. L. 273 µ.

{103}The central nodule is scarcely evident, probably because it is not so

thick as in other forms. The outline is near to that of N. mesogongyla and

certain forms of N. nobilis, differing from the latter in the median line,

striæ and band which is wider than that of P. latevittata var. domingensis

Cl.

Hammonton Pond, N. J.

Pl. 28, Fig. 2.

A very beautiful form which I cannot find described or figured. It does not

appear to be N. major var. turgidula Cl., which has a narrow band. In the

fossil deposit from Hopkinton, N. H., valves occur similar in outline but

smaller.

PINNULARIA NOBILIS EHR.

Valve slightly gibbous in the middle and at the ends; median line complex;

striæ, 4 or 5 in 10 µ, slightly convergent or parallel at the ends, crossed

by a band one-third as wide as the length of the striæ. L. ? to 350 µ.

Blue clay. Fresh water.

Pl. 28, Fig. 1.

PINNULARIA DACTYLUS EHR.

Valve broad, linear, slightly gibbous in the middle; ends broad, rounded;

median line not complex, sinuous; striæ, 4 or 5 in 10 µ, crossed by a very

broad band. L. ? to 300 µ.

_Navicula gigas_ A. S.

Blue clay. Fresh water.

Pl. 28, Fig. 3.

Forms occur which are with difficulty assigned to either nobilis or

dactylus.

PINNULARIA DACTYLUS VAR. DARIANA (A. S.) CL.

Valve linear-lanceolate, obtuse; axial area broad, less than one-third the

width of the valve; striæ, 6 in 10 µ, crossed by a broad band. L. 220 µ.

Absecon, N. J.

Pl. 29, Fig. 3.

PINNULARIA DACTYLUS VAR. DEMERARÆ CL.

Valve elliptical-lanceolate, with sub-cuneate ends; axial area lanceolate,

broad in the middle; median line flexuose; striæ radiate throughout, 6 in

10 µ. L. 150 µ.

Blue clay.

Pl. 29, Fig. 10.

PINNULARIA GENTILIS (DONK.) CL.

Valve linear, with rounded ends; axial area about one-fourth the diameter

of the valve; striæ radiate in the middle, convergent at the ends, 7 in 10

µ, crossed by a broad indistinct band.

Fresh water. Not common.

Pl. 29, Fig. 1.

PINNULARIA TRIGONOCEPHALA CL.

Valve linear, gibbous in the middle and at the cuneate ends; axial area

wider between the middle and the ends, dilated to an elliptical space in

the middle; striæ, 6 in 10 µ. L. 145 µ.

Blue clay.

Pl. 29, Fig. 8.

{104}PINNULARIA VIRIDIS NITZSCH

Valve linear-elliptical, with rounded ends; axial area narrow, widened in

the middle; striæ, 6 to 7 in 10 µ, crossed by a band as wide as one-third

the length of the striæ.

Common in fresh water.

Pl. 29, Fig. 2.

Quite variable in size. Approaches P. major by intermediate forms as in

Fig. 9, Pl. 29.

PINNULARIA VIRIDIS VAR. FALLAX CL.

Valve linear, with rounded ends; axial area narrow, slightly widened in the

middle; striæ sometimes unilaterally interrupted, nearly parallel, 10 in 10

µ.

Elm, N. J.

Pl. 29, Fig. 4.

In Fig. 2, Pl. 30, a form is represented which corresponds closely to

Navicula viridis var. B, of Wm. Smith. It is given as synonymous with var.

fallax; it is bilaterally interrupted. Blue clay.

PINNULARIA VIRIDIS VAR. ?

Valve linear-elliptical, with rounded ends; axial area narrow, widened in

the middle to a transverse fascia which is sometimes unilateral; striæ, 14,

in the middle, divergent, convergent at the ends and closer, crossed by a

narrow band. L. 45-60 µ. Fascia sometimes absent or very narrow.

Northbrook, Pa.

Pl. 30, Fig. 17 (represents a form with wider area than usual).

PINNULARIA VIRIDIS VAR. CAUDATA N. VAR.

Valve elliptical-lanceolate, with sub-rostrate ends; axial area narrow,

widened to an orbicular space in the middle; striæ radiate in the middle,

11-12 in 10 µ, convergent and closer at the ends, crossed by a narrow band;

median line with very long terminal fissures; terminal nodules noticeable

because of the thickening of the edges of the terminal striæ. L. 43 µ.

Fresh water, Newtown Square. Not common.

Pl. 30, Fig. 18.

PINNULARIA SOCIALIS (PALMER)

Valve linear, with rounded ends; axial area broad, one-third the width of

the valve; striæ slightly radiate in the middle, convergent at the ends,

elsewhere parallel, 8 in 10 µ, crossed by an indistinct band about

one-third the length of the striæ. L. 60-120 µ.

This species, discovered by Mr. Palmer near Media, Pa., is remarkable for

the grouping of the frustules "held with girdle sides together by a

siliceous cementing of valve edges and enclosed in a common coleoderm." The

usual number included in a group is four, but sometimes six or eight are

noticed. The frustules adhere near their ends and are so firmly fastened

that boiling in nitric acid and bichromate of potash for fifteen minutes

will not separate them.

_Navicula socialis_ Palmer (Proc. Acad. Nat. Sci., Phila., 1910, p. 460,

Pl. 35).

Media, Pa.

Pl. 29, Fig. 5.

{105}PINNULARIA ÆSTUARII CL.

Valve linear, with rounded ends; axial area broad, less than one-third the

width of the valve; central area a transverse fascia; striæ, 7 in 10 µ,

parallel except at the ends where they are slightly convergent; median line

flexuose, with short, terminal semicircular fissures. L. 85 µ.

Port Penn, Delaware River. Rare.

Pl. 29, Fig. 6.

GRACILLIMÆ

PINNULARIA MOLARIS (GRUN.) CL.

Valve very convex, linear, with sub-cuneate ends; axial area narrow,

expanded in the middle to a transverse fascia reaching the margin; striæ

divergent in the middle, convergent at the ends, 16 in 10 µ. L. 60 µ.

Fresh water.

Pl. 29, Fig. 15.

PINNULARIA LEPTOSOMA GRUN.

Valve linear, rounded at the ends; axial area narrow; central area a broad

transverse fascia; striæ slightly divergent in the middle and convergent at

the ends, 17 in 10 µ in the middle, closer at the ends. L. 56 µ.

Fresh water. Not common.

Pl. 30, Fig. 10.

CAPITATÆ

PINNULARIA MESOLEPTA EHR.

Valve linear, with triundulate margins and capitate ends; axial area

narrow, widened in the middle; striæ divergent in the middle, convergent at

the ends, about 12 in 10 µ. L. 34 µ.

Common in fresh water.

Pl. 29, Fig. 13.

PINNULARIA MESOLEPTA VAR. STAURONEIFORMIS GRUN.

Valve triundulate, capitate; axial area narrow, widened in the middle to a

transverse fascia, broader at the margin; striæ strongly divergent in the

middle and convergent at the ends, 9-10 in 10 µ. L. 70 µ.

Pavonia, N. J., artesian well. Fresh water.

Pl. 30, Fig. 20.

PINNULARIA SUBCAPITATA GREG.

Valve linear or linear-elliptical, with sub-capitate ends; axial area

distinct, widened to a transverse fascia in the middle; striæ divergent in

the middle, convergent at the ends, 13 in 10 µ. L. 32 µ.

Fresh water.

Pl. 29, Fig. 20.

{106}PINNULARIA SUBCAPITATA VAR. PAUCISTRIATA GRUN.

Valve linear-elliptical, with rounded ends; axial area gradually widened

into a broad, transverse fascia; striæ divergent in the middle, convergent

at the ends, 11-12 in 10 µ. L. 47 µ.

Fresh water.

Pl. 30, Fig. 16.

PINNULARIA TERMES (EHR.) A. S.

Valve linear, with concave margins and rostrate-capitate ends; axial area

narrow, widened in the middle to an orbicular or sub-quadrate space; striæ

divergent in the middle, scarcely, if at all, convergent at the ends, 10 in

10 µ.

Pensauken, N. J., artesian well.

Pl. 29, Fig. 17.

This is, I believe, the form figured by Schmidt (Atlas, Pl. 45, Fig. 67).

Cleve refers it to Pinnularia interrupta forma biceps, in which the central

space is rhomboid.

PINNULARIA TERMES VAR. STAURONEIFORMIS V. H.

Valve linear, with concave margins and capitate-rostrate ends; axial area

narrow, widened into a rhomboidal fascia, reaching the margin; striæ, 10 in

10 µ, divergent in the middle, convergent at the ends.

_Pinnularia interrupta forma stauroneiformis_ Cl.

Fresh water.

Pl. 29, Fig. 14.

PINNULARIA APPENDICULATA (AG.) CL.

Valve linear, with subcapitate ends; axial area narrow; central area a

transverse fascia; striæ divergent in the middle, convergent at the ends,

16 in 10 µ. L. 43 µ.

Fresh water. Marl pits, Lenola, N. J. (Palmer).

Pl. 29, Fig. 18.

PINNULARIA BRAUNII GRUN.

Valve linear-lanceolate, with capitate ends; axial area gradually widened

toward the middle and expanded into a fascia reaching the margin; striæ

divergent in the middle, convergent at the ends, 11 in 10 µ. L. 52 µ.

Pensauken, N. J., artesian well.

Pl. 29, Fig. 16.

PINNULARIA MICROSTAURON (EHR.) CL.

Valve convex, linear, tapering to sub-cuneate or sub-rostrate ends; axial

area very narrow; central area a broad fascia; striæ divergent in the

middle, convergent at the ends, 12 in 10 µ. L. 35 µ.

Pavonia, N. J., artesian well.

Pl. 29, Fig. 19.

This form does not exactly correspond to Cleve's diagnosis, as the ends are

not broad. All species in the group Capitatæ are quite variable.

{107}DIVERGENTES

PINNULARIA DIVERGENS VAR. ELLIPTICA GRUN.

Valve linear, with rounded ends; axial area widened in the middle to a

transverse fascia; striæ, 9 in 10 µ, divergent in the middle, convergent at

the ends. L. 150 µ.

Fresh water. Not common in this locality.

Pl. 31, Fig. 13.

PINNULARIA CARDINALICULUS CL.

Valve linear, with rounded ends; axial area wide, less than one-third the

width of the valve, expanded to a transverse fascia; striæ divergent in the

middle and slightly convergent at the ends, 9 in 10 µ. L. 97 µ.

Blue clay.

Pl. 30, Fig. 1.

As a rule, the median fissures in Pinnularia are turned inwards on the side

of the longer edge of the terminal fissures, but not always. In this

specimen the median fissures are turned slightly toward the side of the

shorter edge of the terminal fissures.

PINNULARIA LEGUMEN EHR.

Valve linear, with more or less triundulate margins and broad, capitate

ends; axial area less than one-fourth the width of valve, widened in the

middle; striæ strongly divergent in the middle and convergent at the ends,

10 in 10 µ. L. 84 µ.

Fresh water. May's Landing, N. J.

Pl. 30, Fig. 3.

PINNULARIA LEGUMEN VAR. ?

Valve as in type, but with a transverse fascia; striæ, 10 in 10 µ, curved

or bent near the ends. L. 84 µ.

This form is not var. florentina Grun.

May's Landing, N. J. (with the type).

Pl. 30, Fig. 4.

PINNULARIA BRÉBISSONII (KUETZ.) CL.

Valve linear-elliptical, with rounded ends; axial area narrow, widened into

a transverse fascia which is usually broader at the ends; striæ divergent

in the middle, convergent at the ends, about 12 in 10 µ. L. 40-60 µ (Cl.).

Fresh water. Common.

Pl. 29, Fig. 12; Pl. 31, Fig. 11.

Variable in outline.

PINNULARIA MORMONORUM (GRUN.)

Valve linear, with rounded ends; striæ divergent in the middle, convergent

at the ends, 10 in 10 µ; axial area rhombic-lanceolate, widened to a fascia

usually reaching the border. L. 62 µ.

_Navicula mormonorum_ Grun.

Common near Willistown, Pa.

This form is regarded by Cleve as P. brébissonii, but the axial area

appears to distinguish it. The valves are sometimes narrowed in the middle.

Pl. 29, Fig. 11.

{108}BREVISTRIATÆ

PINNULARIA ACROSPHÆRIA (BRÉB.) CL.

Valve linear, gibbous in the middle and at the ends; axial area about half

the width of the valve; median line with approximate central pores; median

area punctate; striæ nearly parallel, radiate at the ends, 9 in 10 µ. L.

32-180 µ (Cl.).

Blue clay. Recent, fresh water.

Pl. 30, Fig. 7.

PINNULARIA ACROSPHÆRIA VAR. TURGIDULA GRUN. ?

Valve strongly gibbous in the middle; ends rounded; striæ, 12-13 in 10 µ.

L. 54 µ.

Blue clay, Gloucester, N. J., artesian well.

Pl. 30, Fig. 8.

PINNULARIA BLANDITA N. SP.

Valve linear, gibbous in the middle, and with rounded ends; striæ radiate

in the middle, convergent at the ends, 13 in 10 µ; axial area about

one-fourth the width of the valve, widened in the middle; median line with

small semicircular terminal fissures. L. 65 µ.

Pavonia, N. J., artesian well. Rare.

Pl. 30, Fig. 25.

PINNULARIA PARVA (EHR.) CL. VAR. ?

Valve linear, tapering to the subcapitate ends; axial area broad,

lanceolate; median line with approximate central pores and semicircular

terminal fissures; striæ slightly divergent in the middle and convergent at

the ends, 12 in 10 µ. L. 58 µ.

Differs from the type in having finer striæ.

Atco, N. J.

Pl. 30, Fig. 14.

PINNULARIA NODOSA FORMA CAPITATA CL.

Valve triundulate, with capitate ends; axial area about one-fourth the

width of valve; striæ parallel, convergent at the ends, 10 in 10 µ,

sometimes interrupted in the middle. L. 47 µ.

Fresh water. Common.

Pl. 30, Figs. 15 and 19.

PINNULARIA POLYONCA (BRÉB.) LEWIS

Valve with triundulate margins, more inflated in the middle, with capitate

ends; axial area very broad; striæ marginal, short, 9 in 10 µ, divergent in

the middle, convergent at the ends. L. 97 µ.

Kirkwood Pond, N. J.

Pl. 30, Fig. 21.

The description of Kuetzing (Species Algarum, p. 85), where he states that

the margins are "triundulate, the median inflation larger, apices

rounded-capitate," appears to sufficiently distinguish this species, which

I believe to be the same as Brun's Navicula peripunctata, except that the

form figured (Espèces Nouvelles, Pl. 16, Fig. 11) is interrupted in the

middle, a common variation in these forms. Cleve makes Navicula polyonca

Bréb. equal Pinnularia mesolepta, but at the same time he considers Lewis'

form and also Brun's as equivalent to Navicula formica Ehr., and calls it

Pinnularia nodosa var. formica Ehr. P. mesolepta has a narrower area than

nodosa. I adhere to Lewis' identification, as in any case it is the form

here figured and is nearly, if not quite, the same as Brun's species.

{109}DISTANTES

PINNULARIA LATA (BRÉB.) WM. SM.

Valve linear-elliptical, broad; axial area broad, widened in the middle;

striæ slightly radiate in the middle, 3 in 10 µ; median line oblique, the

terminal fissures hook-shaped. L. 86 µ.

Blue clay. Not uncommon.

Pl. 30, Fig. 23.

PINNULARIA BOREALIS EHR.

Valve linear, with rounded or sub-truncate ends; axial area about

one-fourth the width of the valve, widened in the middle; median line with

large hook-shaped terminal fissures; striæ, 4 or 5 in 10 µ. L. 54 µ.

Blue clay. Occasional in fresh water in a smaller form. Specimens occur

intermediate between P. lata and P. borealis.

Pl. 30, Fig. 22; Pl. 31, Fig. 12.

PINNULARIA BOREALIS VAR. SCALARIS (EHR.) CL.

Valve narrow, linear; axial area broad, widened into a transverse fascia;

striæ, 8 in 10 µ. L. 32 µ.

Fresh water.

Pl. 30, Fig. 24.

TABELLARIÆ

PINNULARIA STOMATOPHORA (GRUN.) CL.

Valve linear, with rounded ends; axial area less than one-third the width

of the valve, gradually widened in the middle to a transverse fascia; on

each side of the central nodule is a lunate space; striæ divergent in the

middle, convergent at the ends, 13 in 10 µ; terminal fissures very long,

bayonet shaped. L. 75 µ.

Cleve describes a variety continua as not interrupted. In some forms the

fascia is marked by very faint, short striæ on the margin.

Fresh water. Newtown Square.

Pl. 30, Fig. 12.

PINNULARIA GIBBA (KUETZ.) V. H.

Valve linear, tapering to the subcapitate ends; axial area dilated in the

middle; striæ, 10-11 µ, divergent in the middle, convergent at the ends. L.

80 µ.

Fresh water.

Pl. 30, Fig. 5.

PINNULARIA MESOGONGYLA (EHR.) CL.

Valve linear, gibbous in the middle, ends subcapitate; axial area narrow,

widened in the middle to a large orbicular space; striæ strongly divergent

in the middle, convergent at the ends, 11 in 10 µ. L. 60 µ.

Fresh water. Common.

Pl. 30, Fig. 6.

{110}PINNULARIA STAUROPTERA (GRUN.) CL.

Valve linear, with slightly triundulate margins tapering to the subcapitate

ends; axial area more than one-third the width of the valve, slightly

widened in the middle; median line with approximate central pores and

semicircular terminal fissures; striæ divergent in the middle, convergent

at the ends, 11 in 10 µ. L. 82 µ.

May's Landing, N. J.

Pl. 30, Fig. 13.

Some of the forms are more triundulate than the specimen figured.

PINNULARIA STAUROPTERA VAR. INTERRUPTA CL.

Valve linear, tapering to the subcapitate ends; axial area broad, widened

in the middle to a transverse fascia; striæ divergent in the middle,

convergent at the ends, 10 in 10 µ; median pores approximate. L. 118 µ.

Schuylkill River.

Pl. 30, Fig. 11.

PINNULARIA TABELLARIA (EHR.) CL.

Valve linear, gibbous in the middle and tapering to the subcapitate ends;

axial area about one-third the width of the valve, widened in the middle;

median line with approximate central pores and bayonet-shaped terminal

fissures; striæ sometimes unilaterally interrupted, divergent in the

middle, strongly convergent at the ends, 9 in 10 µ. L. 138 µ.

Blue clay. Rare.

Pl. 30, Fig. 9.

The form here figured has coarser striæ than in the type which is also

usually more capitate.

P. legumen has triundulate margins, P. mesogongyla has an orbicular space,

while P. gibba has the space widened. According to Cleve, P. gibba has

approximate central pores, as has also P. mesogongyla. In what I have

considered to be P. legumen, the central pores are more approximate than in

the other two species mentioned. In fact, all of the three resemble each

other closely, and are variously named by different authors. The form of P.

gibba here figured, which may be P. stauroptera, is not the typical form of

Wm. Smith, which has a narrow area and central space. There are, however,

among the typical specimens in H. L. Smith's Type Slide No. 275, smaller

valves which show a resemblance.

MARINÆ

PINNULARIA RECTANGULATA (GREG.) CL.

Valve linear, with abruptly rounded ends; axial area very narrow; central

area large, somewhat quadrate; striæ, 7-8 in 10 µ. L. 78 µ.

_Navicula rectangulata Greg._

Shark River, N. J.

Pl. 29, Fig. 7.

{111}EPITHEMIA BRÉB. (1838)

(epithema, a cover or lid)

Frustules epiphytic, solitary, sometimes geminate, adherent on the ventral

side at the ends; in zone view rectangular, sometimes tumid in the middle.

Valve arcuate, having an interior costate stratum or transverse septa

extending to the girdle, often detached, and an exterior valve surface with

transverse rows of puncta. Central and terminal nodules not easily seen; in

some species a true raphe is indicated.

The resemblance between Epithemia and Eunotia has been already mentioned.

In the shape and striation of the valves there is an approach to Cymbella.

The genus is divided into two groups, one in which the costæ alternate with

double rows of puncta, as in E. turgida, and the other in which the rows of

puncta are more than two.

The endochrome usually consists of a band lying along the ventral zone and

extending in two flaps on the valves.

EPITHEMIA TURGIDA (EHR.) KUETZ.

Valve arcuate, with ends subcapitate; costæ radiate, 4 in 10 µ, alternating

with double rows of puncta. Median nodule central, the raphe curved toward

the ventral edge which it closely follows.

Parasitic on algæ. Very common in fresh water, especially in ponds. In the

figure the valve is asymmetrical with respect to the transverse axis, an

unusual condition.

Pl. 31, Fig. 14.

EPITHEMIA ARGUS KUETZ.

Valve with dorsal margin convex, and ventral margin nearly straight; ends

rounded, constricted; costæ robust, alternating with more than two rows of

puncta; zone view rectangular, the thickened ends of the costæ forming

large nodules in a row along the edge of the valve next to the connecting

zone.

_Cystopleura argus_ (Ehr.) Kunze.

Common in fresh water.

Pl. 31, Figs. 15 and 21.

EPITHEMIA ARGUS VAR. ?

Valve strongly arcuate on the dorsal side and concave on the ventral;

tapering to the rounded but not produced ends; costæ at unequal distances,

about 2 in 10 µ; granules in transverse rows, 8 in 10 µ. L. 100 µ.

Pensauken, N. J., artesian well.

Pl. 31, Fig. 16.

EPITHEMIA MUELLERI A. S. ?

Valve broad, convex, slightly arcuate, with obtuse, somewhat constricted

apices; costæ about 4 in 10 µ; striæ, 12-14 in 10 µ; in zone view the

outline is rectangular, slightly tumid in the middle. L. 78 µ.

Blue clay.

Pl. 31, Fig. 17.

{112}EPITHEMIA ZEBRA VAR. PROBOSCIDEA (KUETZ.) GRUN.

Valve convex on the dorsal, concave on the ventral side; costæ, 3-4 in 10

µ, slightly radiating; apices recurved, capitate.

Blue clay.

Pl. 31, Fig. 18.

EPITHEMIA GIBBERULA VAR. PRODUCTA GRUN.

Valve narrow, lunate, with produced and arcuate apices; costæ radiate, 3-4

in 10 µ; striæ, 16-18 in 10 µ, punctate. L. 58 µ, usually smaller.

Blue clay.

Pl. 31, Fig. 19.

EPITHEMIA MUSCULUS KUETZ.

Valve short, strongly arcuate on the dorsal, concave on the ventral side;

apices slightly produced; costæ radiate, about 5 in 10 µ; striæ, 15 in 10

µ, punctate. L. 20-60 µ.

Shark River, N. J.

Pl. 31, Fig. 20.

EPITHEMIA MUSCULUS VAR. CONSTRICTA (BRÉB.) V. H.

Frustule elliptical, slightly constricted in the middle. Valve convex on

the dorsal, straight on the ventral side; costæ about 4 in 10 µ; striæ

about 18 in 10 µ, finely punctate. L. 45 µ.

_Epithemia succinta_ Bréb.

New Rochelle, N. Y.

Pl. 31, Fig. 22.

RHOPALODIA MUELLER (1885)

(Rhopalodes, like a war club)

Frustule in zone view linear, linear-elliptical (in our species), or

clavate. Valve reniform or lunate; a raphe, not visible in some species in

the usual position of the valve, is found along the convex edge or keel.

Median and terminal nodules, although very small, can be determined. The

name is more appropriate to the African species which are clavate. Two

species only are found in this locality.

The chief distinction between Epithemia and Rhopalodia is in the position

of the raphe and the nodules. In R. gibba and R. ventricosa the costæ are

parallel and not radiate since the valves are not lunate.

Chromatophore a single band irregularly divided.

RHOPALODIA GIBBA (KUETZ.) MUELLER

Valve linear, arcuate on the dorsal, straight on the ventral side, reflexed

at the extremities. Costæ, 6-7 in 10 µ; striæ about 14 in 10 µ. L. 80-200

µ.

Fresh water. Common.

Pl. 31, Fig. 23.

In this species the raphe and nodules can be seen only when the valve is

examined at right angles to its usual position.

{113}RHOPALODIA VENTRICOSA (KUETZ.) MUELLER

Valve gibbous in the middle on the dorsal side, straight on the ventral

side, with reflexed apices; costæ, 7 in 10 µ; striæ, 14-16 in 10 µ. L.

40-100 µ.

The median nodule appears as a minute depression in the middle of the

dorsal side. The two species usually occur together.

_Epithemia gibba_ var. _ventricosa_ Kuetz.

Pl. 31, Fig. 24.

SURIRELLOIDEÆ

The Surirelloideæ are usually understood to include the genera Surirella,

Podocystis, Cymatopleura and Campylodiscus, all of which resemble each

other more or less, either in having a keel or markings like the divisions

of the keel in Surirella and a median line, or pseudoraphe. The genus

Nitzschia also has a keel, but it does not border each side of the valve as

in Surirella, being found either near one margin or between it and the

centre. Certain of the Surirellæ are allied to the group Tryblionella of

the Nitzschiæ, while forms of Stenopterobia are distinguished with

difficulty from the group Sigmata.

The following arrangement, therefore, is intended to include all genera

having a keel or something which resembles it.

_Hantzschia._--Valve asymmetrical; keels of the two valves opposite each

other.

_Nitzschia._--Valve asymmetrical; keels not (usually) opposite each other.

_Surirella._--Valve usually symmetrical; a keel on each border.

_Cymatopleura._--Valve without an elevated keel, but with markings like

those of Surirella; undulated in zone view.

_Campylodiscus._--Valves saddle-shaped.

HANTZSCHIA GRUN. (1877)

(named after C. A. Hantzsch)

Valve arcuate, with rostrate ends; keel puncta short, prolonged into costæ

or extending across the valve; median nodule rudimentary; the keels of the

two valves opposite each other.

Distinguished from Nitzschia chiefly by the position of the keels.

According to Mereschkowsky, however, two species of Nitzschia, N.

lanceolata and N. spectabilis, show the same peculiarity.

Chromatophores four, two on each of the zones (Mereschkowsky).

HANTZSCHIA AMPHIOXYS (EHR.) GRUN.

Valve slightly arcuate, with rostrate apices; keel puncta, 8 in 10 µ; striæ

transverse, 16-18 in 10 µ, punctate. L. 60 µ.

Quite variable.

Fresh water.

Pl. 32, Fig. 9.

{114}HANTZSCHIA AMPHIOXYS VAR. MAJOR GRUN.

Valve as in type, but the keel puncta are 5 in 10 µ and the striæ are 11-12

in 10 µ. L. 71 µ.

H. amphioxys var. major Grun. is stated to be 120 µ in length. The present

form is smaller but corresponds in puncta and striation. Van Heurck remarks

that it approaches H. virgata.

Abundant in sand ripples on the beach at Cape May, N. J.

Pl. 39, Fig. 4.

Fig. 6, Pl. 39, is drawn from an authentic specimen of Wm. Smith's

Nitzschia amphioxys, from England, and is introduced for comparison. The

central nodule is not evident.

Fig. 3, Pl. 39, is from a specimen from an unknown locality. The keel

puncta are 6 and the striæ 16 in 10 µ.

HANTZSCHIA VIRGATA (ROPER) GRUN.

Valve arcuate on the dorsal side, nearly straight on the ventral side, with

rostrate, recurved apices; keel puncta prolonged to one-third the width of

the valve, 4 in 10 µ; transverse striæ, 9-10 in 10 µ. L. 115 µ.

Shark River, N. J. (Kain).

I have not been able to find this form on our coast. The figure is drawn

from a specimen from another locality.

Pl. 32, Fig. 23.

HANTZSCHIA MARINA (DONK.) GRUN.

Valve with dorsal margin slightly arcuate, ventral margin straight; apices

rostrate and recurved; keel puncta, 6 in 10 µ, prolonged into costæ across

the entire valve; transverse striæ, 12 in 10 µ, in double rows of

alternating puncta between the costæ. L. 106 µ.

_Epithemia marina_ Donkin.

Along the coast.

Pl. 32, Fig. 22.

NITZSCHIA HASSALL (1845), em. GRUN. (1880)

(named after Christian L. Nitzsch, of Halle)

Frustules usually free, sometimes enclosed in tubes or united into a

filament. Valves keeled, the keels of the two valves usually diagonally

opposite (see Hantzschia); keel puncta short or prolonged.

According to Mereschkowsky, there are at least two endochrome plates placed

transversely on the zones; sometimes there are from four to six plates, in

one species twenty granules and in another no trace of any endochrome

whatever.

The following analysis is that of Grunow as given in Cleve and Grunow's

"Arctic Diatoms," and adopted and illustrated by Van Heurck in his

"Synopsis."

GROUPS

1. _Tryblionella._--Keel very excentric, valve often folded; keel puncta

indistinct, usually the same in number as the striæ.

2. _Panduriformes._--Valve broad, constricted in the middle, with more or

less evident fold; keel very near the edge; keel puncta quite evident or

apparently wanting.

{115}3. _Apiculatæ._--Keel very near the edge; valve linear or somewhat

narrower in the middle; striæ on the longitudinal fold fainter than on the

remaining surface, or wanting; puncta not in quincunx.

4. _Pseudo-Tryblionella._--Keel more or less close to the edge; valve with

a more or less deep longitudinal fold over which the striæ are spread in

the same way as over the remaining surface; keel puncta always distinct.

5. _Circumsutæ._--Valve with more or less wide longitudinal fold; keel very

excentric; keel puncta quite evident; surface of valve irregularly punctate

and also traversed by rows of delicate puncta which belong to a different

layer of the valve.

6. _Dubiæ._--Like the group Pseudo-Tryblionella, but the valves are not so

much folded; frustules sometimes narrowed in the middle. The separation of

species is difficult and, in part, doubtful. Keel excentric.

7. _Bilobatæ._--Like the group Dubiæ, but with more central keel and so

forming a transition to the group Pseudo-Amphiprora; valves without

longitudinal folds.

8. _Pseudo-Amphiprora._--Valve with quite central, sharp keel, arcuate,

without longitudinal fold; keel puncta always evident; frustule narrowed in

the middle with more or less marked central nodule.

Includes two species not found in this locality.

9. _Perrya._--Valve arched with very sharp central keel; not narrowed in

the middle; keel puncta mostly on short or long lines which are sometimes

interrupted.

Includes six species not found in this locality.

10. _Epithemioideæ._--Keel excentric; keel puncta extended into costæ

across the entire valve.

11. _Grunowia._--As in the group Epithemioideæ, except that the costæ are

shorter, not extending across the valve; keel very excentric.

12. _Scalares._--Like Grunowia, but with sharper, somewhat excentric keel;

transverse section of frustule quadrangular.

13. _Insignes._--Like Scalares, but with more central keel so that many of

the forms are near the group Perrya; frustule somewhat sigmoid.

14. _Bacillaria._--Keel central or nearly so; valve somewhat arched; keel

sharp, as in the group Insignes.

15. _Vivaces._--Keel moderately excentric; valve, according to position,

semi-lanceolate, with keel puncta in short rows, or lanceolate with quite

central keel. The valves have in many positions a resemblance to

Hantzschia, so that N. vivax frequently becomes confounded with a form of

H. amphioxys. The median keel puncta are not distant and a central nodule

is not evident as is the case in all species of Hantzschia.

16. _Spathulatæ._--Like the group Bacillaria, but usually with very

delicate striated valves; keel in valve view usually bordered with two

parallel lines.

17. _Dissipatæ._--Like Vivaces and Spathulatæ, but with smaller central

keel and without parallel lines. Valves usually small, very delicately

striated; no central nodule.

18. _Sigmoideæ._--Keel quite central; no parallel lines; frustule sigmoid;

valve without longitudinal furrow; keel puncta not extended; no central

nodule evident.

19. _Sigmata._--Like Sigmoideæ, but with a more excentric keel.

20. _Obtusæ._--Like Sigmata, with a more or less excentric keel which has

in the middle a small bending to the inside; middle keel puncta somewhat

more distant than the others, and between them a central nodule evident.

{116}21. _Spectabiles._--Valve large, slightly arcuate, with excentric

keel; no longitudinal folds; keel puncta somewhat extended over the valve

but much less than in the group Insignes, and often scarcely perceptible.

22. _Lineares._--Keel somewhat excentric, but less than in Spectabiles;

frustule straight, sometimes a little constricted in the middle, so that a

transition is shown to the groups Dubiæ and Bilobatæ. Valve without

longitudinal fold; keel puncta round or somewhat angular, scarcely

extended.

23. _Lanceolatæ._--Valve lanceolate, linear-lanceolate or rarely

elliptical, with very excentric keel; not folded; keel puncta not extended.

24. _Nitzschiella._--Valve with excentric keel and long, produced apices.

TRYBLIONELLA

NITZSCHIA TRYBLIONELLA HANTZSCH

Valve elliptical-lanceolate, with subacute apices; longitudinal fold well

marked; striæ coarse, transverse, 5 in 10 µ; indistinct puncta intermediate

between the striæ. L. 45 µ. Quite variable.

Blue clay.

Pl. 32, Fig. 8.

NITZSCHIA GRANULATA GRUN.

Valve elliptical or elliptical-lanceolate; striæ in double rows, each row

of three or four small puncta along the margin and rows of large puncta

about 6 in 10 µ across the valve. L. 28-44 µ.

Blue clay. Along the coast.

Pl. 32, Fig. 3.

NITZSCHIA NAVICULARIS (BRÉB.) GRUN.

Valve elliptical-lanceolate, with acute apices; striæ on one side a double

row of large and small puncta, and on the other side radiate short rows of

large puncta, 7 in 10 µ; middle of valve hyaline. L. 35-60 µ.

Blue clay. Not common.

Pl. 32, Fig. 4.

NITZSCHIA COMPRESSA (BAIL.)

Valve elliptical-lanceolate, sometimes acuminate; striæ, 6 or 7 in 10 µ,

coarsely punctate. L. 56 µ.

_Pyxidicula compressa_ Bailey.

_Nitzschia punctata_ (Wm. Sm.) Grun.

_Tryblionella punctata_ Wm. Sm.

Common along the coast.

Pl. 39, Fig. 7.

Var. minor (H. L. Smith).--Valve acuminate; striæ, 8 in 10 µ. L. 22 µ.

_Pyxidicula compressa_ var. _minor_ H. L. Smith, Type Slide No. 431.

Pl. 39, Fig. 8.

The smaller forms occur northward, while the larger are found southward.

This is unquestionably Bailey's form, as indicated by his figure and by the

fact that it is found everywhere along the coast. Wm. Smith's T. punctata

is the same species, although the puncta are smaller.

{117}PANDURIFORMES

NITZSCHIA PANDURIFORMIS GREG.

Valve elliptical, constricted in the middle, with sub-cuneate apices;

longitudinal fold, with a punctate longitudinal line; striæ transverse and

oblique, 15 in 10 µ; keel puncta, 6 in 10 µ. L. 108 µ.

Along the coast. More often found southward.

Pl. 39, Fig. 2.

NITZSCHIA PANDURIFORMIS VAR. MINOR GRUN.

Valve elliptical, constricted in the middle, with cuneate apices; keel

puncta, 9 in 10 µ; striæ in transverse and oblique lines about 20 in 10 µ;

longitudinal fold bordered by a punctate line. L. 34 µ.

Pavonia, N. J., artesian well.

Pl. 32, Fig. 5.

The var. continua Grun. is reported as occurring in Shark River. It varies

in having the longitudinal fold punctate. It is also usually smaller than

var. minor.

APICULATÆ

NITZSCHIA APICULATA (GREG.) GRUN.

Valve oblong-linear, with cuneate-apiculate apices; striæ punctate,

apparently interrupted or pervious, about 18 in 10 µ. L. 26 µ.

Chester River, Md.

Pl. 32, Fig. 6.

The puncta are continued across the valve, but are less distinct on the

fold. The figure shows the entire frustule with the fold on each valve. The

valves are sometimes slightly constricted.

NITZSCHIA ACUMINATA (WM. SM.) GRUN.

Valve linear, sometimes slightly constricted in the middle, with acuminate

apices; longitudinal fold entirely without or with indistinct striæ; keel

puncta not evident; striæ, 14-15 in 10 µ. L. 82 µ.

Port Penn, Delaware River.

Pl. 32, Fig. 13.

NITZSCHIA PLANA WM. SM.

Valve linear; apices acute, slightly constricted in the middle;

longitudinal fold further from the keel than the margin, broad, with

scattered puncta; striæ subtle, irregular, interrupted, about 18 in 10 µ;

keel puncta oblong, 3-6 in 10 µ. L. 100-170 µ.

Blue clay. Along the coast.

Pl. 32, Fig. 2.

{118}PSEUDO-TRYBLIONELLA

NITZSCHIA LITORALIS VAR. DELAWARENSIS GRUN.

Valve linear, with obtusely rounded cuneate ends, scarcely, if at all,

constricted in the middle; longitudinal fold wide; keel puncta, 5 or 6 in

10 µ, sometimes confluent; striæ obscure, about 21 in 10 µ. L. 75 µ.

Delaware River.

Pl. 32, Fig. 12.

This form is drawn from a slide of Christian Febiger containing an

abundance of specimens from Delaware City, and marked "Nitzschia dubia."

CIRCUMSUTÆ

NITZSCHIA CIRCUMSUTA (BAIL.) GRUN.

Valve elliptical, sometimes more than 200 µ in length; longitudinal fold

more or less conspicuous; keel puncta about 4 in 10 µ, the middle distant

with the appearance of a nodule; striæ irregular, subtle, finely punctate,

frequently interrupted.

_Surirella circumsuta_ Bail.

_Tryblionella scutellum_ Wm. Sm.

Common in brackish water.

Pl. 32, Fig. 1.

DUBIÆ

NITZSCHIA DUBIA WM. SM.

Valve linear, scarcely, if at all, constricted in the middle, with cuneate,

produced, apiculate apices, somewhat recurved; keel very excentric; puncta

sometimes partly prolonged, about 9 in 10 µ; striæ, 20-24 in 10 µ. L. 93 µ.

Reported from along the New Jersey coast. I have not seen it. It is

generally regarded as fresh-water. Slides sometimes labelled N. dubia are

in reality N. litoralis var. delawarensis.

Pl. 39, Fig. 5.

The figure is drawn from a specimen from another locality.

BILOBATÆ

NITZSCHIA BILOBATA WM. SM.

Valve linear-lanceolate, constricted in the middle, apiculate at the ends;

keel puncta 6 in 10 µ, prolonged unequally across part of the valve, the

two median sub-remote; striæ, 16 in 10 µ. Frustule oblong, truncate,

constricted in the middle. L. 120 µ.

Shark River, N. J., Chester River, Md.

Pl. 32, Figs. 10 and 11.

EPITHEMIOIDEÆ

NITZSCHIA EPITHEMIOIDES GRUN.

Valve linear, with cuneate, rostrate apices; slightly constricted on the

keel side; keel puncta, 8 or 9 in 10 µ, extending as costæ across the

valve; striæ delicate, 22 in 10 µ. L. 47 µ.

Brackish water, Long Island Sound.

Pl. 32, Fig. 21.

{119}GRUNOWIA

NITZSCHIA TABELLARIA GRUN.

Valve rhomboidal, inflated in the middle; apices produced; keel puncta

extend in costæ across half of the valve, 7 in 10 µ; striæ transverse,

about 22 in 10 µ. L. 20 µ.

_Dimerogramma sinuatum_ Thwaites.

_Nitzschia sinuata_ var. _tabellaria_ (Grun.) V. H.

Schuylkill River. Not common.

Pl. 32, Fig. 7.

SCALARES

NITZSCHIA SCALARIS (EHR.) WM. SM.

Valve linear, with obtusely conical apices; costæ transverse, extending

more or less to one-third the width of the valve, 3 or 4 in 10 µ; striæ, 9

or 10 in 10 µ, punctate. Length of valve quite variable, up to 480 µ

(Cleve).

A well-known form, abundant in salt marshes and more or less brackish

water.

Pl. 33, Fig. 6. (To the right of the figure is an outline of the valve

reduced one-third.)

INSIGNES

NITZSCHIA INSIGNIS GREG.

Valve nearly linear or linear-lanceolate; apices broad, slightly produced,

obtuse; keel puncta extended into short costæ, 4 or 5 in 10 µ; striæ about

14 in 10 µ. Length variable up to 400 µ.

Delaware Bay.

Pl. 33, Fig. 8.

BACILLARIA

NITZSCHIA PAXILLIFER (O. F. MUELLER) HEIBERG

Frustules united in a filament, afterwards free; valve lanceolate with

nearly central keel; keel puncta, 7-9 in 10 µ; striæ about 21 in 10 µ. L.

110 µ.

_Vibrio paxillifer_ O. F. Mueller.

_Bacillaria paradoxa_ Gmelin.

_Nitzschia paradoxa_ (Gmelin) Grun.

Brackish water or streams subject to its influence.

Pl. 33, Figs. 13 and 14.

Otto Frederick Mueller, in 1786, published at Copenhagen a work on

"Infusorial Animalcules," including a description of a Vibrio which he

named paxillifer, obviously alluding to the partially-extended frustules

bearing at the end a tablet-like bundle. Two years later, Gmelin described

the same form as Bacillaria paradoxa, a name still used. Heiberg, however,

in 1863, placed the form under Nitzschia where it properly belongs and

called it Nitzschia paxillifer (O. F. Mueller). I have adopted Heiberg's

name.

Perhaps the most remarkable of all diatoms. Many species possess the power

of motion, which, however, is evident only in the free frustule. In N.

paxillifer, the movement of the frustules occurs without the loss of

continuity or adherence to each other, so that, while at one time the

adnate frustules form a narrow filament, like that of Fragilaria, at

another {120}time they move laterally to their extreme length and form a

thread of frustules adherent at their ends, later resuming their original

position. The motion is repeated at intervals of from five to ten seconds.

No satisfactory explanation of the movement has ever been made. In the

filamentous form the frustules adhere to water-plants.

VIVACES

NITZSCHIA FLUMINENSIS GRUN.

Valve lanceolate, apices produced; keel puncta, 4-6 in 10 µ, partly

extended in short costæ; striæ transverse, 14-15 in 10 µ, punctate; keel

without a pseudo-nodule. L. 73 µ.

Common at Greenwich Point, Philadelphia.

Pl. 32, Fig. 16.

The form here figured is smaller than the type, which is from 130-160 µ in

length.

SPATHULATÆ

NITZSCHIA SPATHULATA BRÉB.

Frustule linear, truncate, dilated at the ends; zone with longitudinal

folds; valve lanceolate, keel central; apices acute, with an elevated

appendage; keel puncta, 5-6 in 10 µ; striæ very fine. L. 56 µ.

Atlantic City and Cape May, N. J. (Lewis).

Pl. 40, Fig. 3.

DISSIPATÆ

NITZSCHIA DISSIPATA (KUETZ.) GRUN.

Valve lanceolate, with sub-rostrate apices; keel excentric; keel puncta

about 6 in 10 µ; striæ, 14 in 10 µ. L. 20-40 µ.

Fresh and brackish water.

Pl. 40, Fig. 7.

SIGMOIDEÆ

NITZSCHIA MACILENTA GREG.

Frustule sigmoid, truncate at the ends; valve linear, with sub-acute apices

and nearly central keel; keel with 5-6 puncta in 10 µ; striæ obscure, about

25 to 28 (?) in 10 µ. Length variable, up to 490 µ.

As the valve is usually seen when the keel is on the margin, the outline

(reduced one-third, shown to the left of the figure) is, as a rule,

sigmoid.

Delaware Bay.

Pl. 33, Fig. 7.

NITZSCHIA VERMICULARIS (KUETZ.) HANTZSCH

Valve linear, sigmoid, attenuated toward the obtuse ends; keel puncta, 9 in

10 µ, quite distinct; striæ very fine. L. 105 µ.

Fresh-water pools.

Pl. 32, Fig. 24; Pl. 33, Fig. 9.

{121}SIGMATA

NITZSCHIA SIGMA (KUETZ.) WM. SM.

Frustule linear, sigmoid; valve linear, slightly sigmoid, tapering to the

sub-acute apices; keel excentric, puncta, 8 in 10 µ; striæ, 20-24 in 10 µ.

L. to 250 µ.

Along the coast.

Pl. 39, Fig. 13.

NITZSCHIA SIGMATELLA GREG.

Valve linear, sigmoid, slightly attenuated toward the obtuse apices; keel

excentric, puncta, 8-10 (?) in 10 µ; striæ delicate, 25-30 in 10 µ. L. to

400 µ. The keel puncta are quite obscure.

_Nitzschia curvula_ Wm. Sm.

_Nitzschia sigma_ var. _curvula_ (Wm. Sm.) De Toni.

Fresh water. Hammonton Pond; May's Landing, N. J.

Pl. 33, Figs. 4 and 5.

Gregory remarks that the keel puncta are seen in some specimens. In both of

the forms figured I have counted 30 striæ in 10 µ, but, after many

examinations, I have not been quite certain about the keel puncta. The

general appearance of the valves in any position is that of a Stenopterobia

or Surirella anceps, with which it occurs.

NITZSCHIA CLAUSII HANTZSCH

Valve linear, slightly sigmoid, tapering to the sub-capitate ends; keel

puncta, 11 in 10 µ; striæ subtle. L. 40 µ.

Abundant in Ridley Creek, Delaware Co. (Palmer).

Pl. 32, Fig. 20.

OBTUSÆ

NITZSCHIA OBTUSA WM. SM.

Frustule sigmoid, rounded at the ends; keel somewhat excentric, inflexed in

the middle, the two median puncta distant; keel puncta, 5-6 in 10 µ; striæ,

26 in 10 µ. L. to 300 µ.

Along the coast.

Pl. 39, Fig. 16.

NITZSCHIA OBTUSA VAR. FLEXELLA H. L. SMITH

Valve more attenuate at the ends than the type and smaller.

Pl. 39, Fig. 14.

NITZSCHIA OBTUSA VAR. SCALPELLIFORMIS GRUN.

Valve linear, with apices unilaterally truncate; keel excentric; keel

puncta, 8 in 10 µ; striæ, 26 in 10 µ. L. 48 µ.

Along the coast.

Pl. 32, Fig. 17.

{122}SPECTABILES

NITZSCHIA SPECTABILIS VAR. AMERICANA GRUN.

Frustule linear, slightly constricted in the middle, with sub-cuneate ends;

valve linear, slightly arcuate, tapering to the sub-rostrate ends; keel

excentric, keel puncta sometimes confluent, 4-6 in 10 µ, prolonged into

short costæ; striæ distinct, 14 in the middle, 18 at the ends in 10 µ (but

variable in different specimens). L. 186 µ.

Blue clay, especially at Tioga St.

Pl. 33, Fig. 3; Pl. 39, Fig. 1.

This is, probably, one of the most beautiful of the Nitzschiæ. It

sometimes, according to De Toni, reaches a length of 520 µ.

Grunow states that his variety is found in the S. Bridgeton deposit. In a

slide of Moeller labelled "Bridgeton, Maine," I find specimens identical in

every respect with the Philadelphia form.

LINEARES

NITZSCHIA LINEARIS (AG.) WM. SM.

Valve linear, slightly inflexed in the middle; keel excentric; keel puncta,

8-9 in 10 µ, the two median distant; striæ about 30 in 10 µ. Frustules in

zone view narrowed toward the ends, truncate. L. 75 µ.

Very common in fresh water.

Pl. 32, Fig. 18. Fig. 20, Pl. 40, a transverse section of frustule.

LANCEOLATÆ

NITZSCHIA PALEA (KUETZ.) WM. SM.

Valve linear-lanceolate, slightly rostrate at the apices; keel puncta, 10

in 10 µ, the median not distant; striæ, 33-36 in 10 µ; zone view linear,

with rounded ends. L. 25-65 µ.

Fresh water.

Pl. 32, Fig. 15.

NITZSCHIA AMPHIBIA GRUN.

Valve lanceolate, apices sometimes slightly produced, rounded; keel puncta,

8-9 in 10 µ; striæ, 16 in 10 µ. L. 20-32 µ.

Fresh water.

Pl. 32, Figs. 14 and 25.

NITZSCHIA COMMUNIS RAB.

Frustule linear, slightly attenuated at the obtuse ends; valve

elliptical-lanceolate, attenuated toward the obtuse ends; keel puncta, 12

in 10 µ; striæ more than 30 in 10 µ. L. 35 µ.

Fresh water.

Pl. 32, Fig. 19.

NITZSCHIA INTERMEDIA HANTZSCH

Valve linear-lanceolate; keel puncta, 8 in 10 µ; striæ about 24 in 10 µ. L.

100 µ.

Crum Creek. Not common.

Pl. 33, Fig. 2.

{123}NITZSCHIELLA

NITZSCHIA LONGISSIMA (BRÉB.) RALFS

Valve linear-lanceolate, with exceedingly long horns or beaks; keel puncta

about 10 in 10 µ; striæ about 16 in 10 µ. L. to 500 µ.

Shark River, N. J.

Pl. 33, Fig. 1.

Forma parva V. H.--Keel puncta, 10-12 in 10 µ. L. 70 µ.

East Park Reservoir, Philadelphia.

Pl. 33, Fig. 10.

Differs from N. closterium (Ehr.) Wm. Sm. in the keel puncta.

The type form occurs in brackish and salt water. The occurrence of the

variety in fresh water is another instance of the finding of presumably

brackish forms in the water supply of the city. If these cases prove to be

unusual, it may be because of one of two reasons. The Schuylkill River,

before the building of the dam at Fairmount, was tidal as far as the Falls

of Schuylkill, and brackish influences, while not now existent, may have

caused the growth of forms which now survive. Another reason may be that

the opening of the locks at Fairmount Dam may cause a slight admission of

brackish forms from tidal water below. The abundance of the brackish

species appears to indicate that the first reason is the more plausible.

NITZSCHIA REVERSA WM. SM.

Valve lanceolate extended into beaks or horns curving in opposite

directions; keel puncta not evident; striæ, "20-26" in 10 µ. L. 70 µ.

Brackish water. Abundant in Duck Creek, Delaware River.

Pl. 33, Fig. 11.

NITZSCHIA ACICULARIS (KUETZ.) WM. SM.

Valve lanceolate, with beaks or horns about half the length of the median

part of the valve; keel puncta, 18 in 10 µ; striæ exceedingly delicate,

"about 40 in 10 µ." L. 45 µ.

Fresh water. Darby Creek.

Pl. 33, Fig. 12.

HOMOEOCLADIA AG. (1827)

(homoios, like, and clados, a branch)

Frustules like Nitzschia, but enclosed in branching or simple tubes.

HOMOEOCLADIA FILIFORMIS WM. SM.

Frustule linear, tumid in the middle, obtuse at the ends; valve

linear-lanceolate, with somewhat acute apices; keel central or nearly so;

keel puncta, 8 in 10 µ; striæ delicate. L. 108 µ.

Fresh and brackish water. Newark, N. J.

Pl. 33, Fig. 15.

{124}SURIRELLA TURPIN (1828)

(named after Dr. Suriray, a physician of Havre)

Valve linear, elliptical or ovate; pseudoraphe linear or lanceolate; a

marginal keel forming wings or alæ seen in zone view; costæ short or

reaching the pseudoraphe, frequently with intercostal striæ more or less

evident.

The genus is divided by Grunow according to the length and form of the

costæ. I include Stenopterobia.

Section 1.--Costæ of nearly equal width throughout, reaching the

pseudoraphe.