Entomostomata, Bl.--_Descr._ Thin, ventricose, oval, or globular, with
a short spire; large aperture terminating in a reflected canal, and
spirally ribbed or grooved external surface; outer lip crenated; inner
lip reflected over part of the body whorl, which terminates in a tumid
varix; epidermis light, horny. Mediterranean and East Indian.--_Obs._
This genus is distinguished from Cassis by the outer lip, which is not
reflected. The species which are not so rotund as the others, as D.
Perdix, Auct. have been separated under the name Perdix, as generic.
Fig. 420, Dolium Maculatum.
DONAX. Auct. _Fam._ Nymphacea, Lam. Conchacea, Bl.--_Descr._ Equivalve,
inequilateral, trigonal, with the anterior side short, straight, plane;
the posterior side elongated, drawn to a narrow, rounded termination;
hinge with two cardinal teeth in one valve, one in the other, and one
or two, more or less remote lateral teeth; ligament external; muscular
impressions two in each valve; palleal impression sinuated
posteriorly.--_Obs._ The Capsæ have not the crenated margins, the short
anterior side, and the distinct lateral teeth, which characterize the
Donaces. Some species of Erycina resemble Donax in general form, but
are at once distinguished by the ligamentary pit in the hinge. Sandy
shores in all climates. Fig. 108, D. cuneatus.
DORSAL. A dorsal shell is one placed upon the back of the animal. The
dorsal margin of a bivalve shell is that on which the hinge is placed;
the opposite margins are termed ventral. The dorsal surface of a spiral
univalve is that which is seen when the aperture is turned from the
observer. The dorsal valve is the uppermost in Brachiopodous bivalves.
The dorsal part of a symmetrical convolute univalve, such as the
Nautilus and Ammonite is that part of the whorls which is at the
greatest distance from the spire, that is, the outer part of the
whorls. Thus the situation of the siphon is said to be dorsal when it
pierces the septum near the outer edge of the whorls. The dorsal part
of symmetrical conical univalves, such as Patella, is the upper part,
on which the apex is placed.
DORSALIA. Lam. (_Dorsum_, the back.) The first family of the order
Annelides Sedentaria, Lam. containing the genera Arenicola, not a
shell, and Siliquaria, fig. 1, which is now considered as a true
mollusc, and placed next to Vermetus.
DOSINA. Schum. VENUS Verrucosa, Casina, and similar species. Fig. 119,
a.
DREISSINA. MYTILUS Polymorphus. Auct. fig. 159. This genus differs from
Mytilus principally in the characters of the animal. The shell is
characterized by a small septiform plate under the hinge within.
Fluviatile, Europe and Africa.
EBURNA. Lam. (_Eburneus_, ivory.) _Fam._ Purpurifera, Lam.
Entomostomata, Bl.--_Descr._ Oval, thick, smooth, turrited,
umbilicated; spire angulated, acute, nearly as long as the aperture;
aperture oval, terminating anteriorly in a canal, posteriorly in a
groove; outer lip slightly thickened with an anterior notch, which
terminates in a spiral fold surrounding the body whorl; umbilicus
generally covered by the thickened columellar lip.--_Obs._ The
beautiful shells called ivory shells, which originally constituted part
of this genus, are now placed in the genus Ancillaria by authors. They
differ from the present genus Eburna, in having the sutures of the
spire covered with a polished enamel. (A. glabrata, fig. 455.) The
Eburnæ resemble in some respects the genus Buccinum, but a glance at
the figure will enable the reader to distinguish a true Eburna from all
other shells. Fig. 426 is Eburna Zeylanica. A catalogue of 9 species is
given in part 20 of the Conchological Illustrations published by the
Author, accompanied by figures of several species.
ECHIDNIS. Montf. Described as a straight, chambered, annulated, fossil
shell, computed from the extremely gradual increase in diameter of the
fragments to be at least sixteen feet long. Found in marble from the
Pyrenees.
ECHINELLA. Sw. A sub-genus of Monodonta. Sw. Malac. page 352.
EFFUSE. (_effundo_, to pour out.) The aperture of an univalve shell is
said to be effuse when there is a notch in the margin which would
suffer a liquid to escape, and thus prevent it being filled to the
brim.
EGEON. Montf. A genus of microscopic Foraminifera.
EGERIA. Lea. (Contrib. to Geol. p. 49, pl. 1.) A genus of fossil
bivalves, described as very variable in form, with or without lateral
teeth, sometimes a crenated margin, &c. The only certain characters
appear to be that they have two diverging cardinal teeth in each valve,
one of which is bifid; and an external ligament. Lea states that the
Egeriæ should be placed between the Sanguinolariæ and the Psammobiæ,
which two latter genera have been united by Sowerby. Fig. 103, E.
Triangulata, from the tertiary formation of Alabama.
ELENCHUS. Humph. A genus composed of TROCHUS Iris, Auct. and other
similarly formed species. It is the same as CANTHARIDUS of Montfort.
ELEPHANT'S TUSK. The common name given by dealers to shells of the
genus Dentalium. _Ex._ D. octogonum, fig. 2.
ELEVATED. A term which is applied by some conchological writers to the
spire of an univalve shell when it consists of numerous whorls drawn
out into a telescopic form. Other authors use the term _elongated_, or
the more simple one '_long_,' to express the degree of elevation.
ELISMA. Leach. A sub-genus of Bulinus. B. acutus, Auct. Gray, Turton,
p. 185.
ELLIPSOLITHES. Montf. ([Greek: Elleipsis], _ellipsis_, oval; [Greek:
lithos,] _lithos_, stone.) A genus composed of Ammonites, which instead
of being regularly orbicular, take an elliptical or oval form. This
character appears to be accidental, as some individuals of the same
species, both of Nautilus and Ammonites, are round, while others are
compressed into an oval form.
ELLIPSOSTOMATA. Bl. ([Greek: Elleipsis], _ellipsis_, oval; [Greek:
stôma], _mouth_.) The third family of the class Asiphonibranchiata, Bl.
The shells of this family are described as of various forms, generally
smooth; the aperture longitudinally or transversely oval, completely
closed by a horny or shelly operculum. This family contains the genera
Rissoa, Phasianella, Ampullaria, Helicina, and Pleuroceras.
ELLIPTICAL. ([Greek: Elleipsis], _ellipsis_.) Oval. Applied to any
shell or part of a shell, having that form.
ELMINEUS. Leach. _Order_, Sessile Cirripedes, Lam.--_Descr._ Four
unequal valves, arranged circularly side by side, forming a quadrate
cone; aperture large, sub-quadrate, irregular; operculum composed of
four valves, in pairs.--_Obs._ This genus differs from Conia in the
structure of the shell, the latter being porous. Fig. 22, Elmineus
Leachii.
ELPHIDIUM. Montf. (Conch. Syst. t. 1. p. 15.) A genus of microscopic
Foraminifera.
EMARGINATED. (_e_, out; _margo_, border.) Notched or hollowed out.
Applied to the edges or margins of shells, when instead of being level
they are hollowed out, as the outer lip of Oliva, fig. 457, at the
base, and the ventral margins of some bivalves.
EMARGINULA. Lam. (_e_, out; _margo_, border.) _Fam._ Calyptracea, Lam.
Branchifera, Bl.--_Descr._ Patelliform, oblong or oval; anterior margin
notched or emarginated; apex posteriorly inclined; muscular impressions
wide.--_Obs._ Emarginula elongata, of some Authors, PARMOPHORUS of De
Blainville is commonly called the Duck's bill limpet, from its shape.
The Emarginulæ may be known from Patellæ and other neighbouring genera,
by the notch or slit in the anterior edge. In the genus Rimula, Defr.
fig. 243, this slit is near the apex, and does not reach the margin.
Recent species occur in all climates, but are not numerous. Fossil
species are still more rare, occurring in the Calc-grossièr, Crag and
Oolite. E. fissurata, fig. 241.
ENA. Leach. A sub-genus of Bulinus. B. Lackhamensis. Mont.
ENDOSIPHONITES. A genus composed of Ammonites, having the siphon close
to the body whorl, fig. 476.
ENDOTOMA. Rafinesque. A genus of microscopic Foraminifera.
ENROULEES. Lam. See CONVOLUTÆ.
ENSATELLA. Sw. A genus consisting of SOLEN ensis, Auct. fig. 60, and
other species similarly curved. _Genus_ ENSIS, Schum.
ENSIS. Schum. SOLEN ensis, Auct. and similar species.
ENTALIS. Defr. DENTALIUM duplicatum, Bl. PHARETRIUM, König. This genus
is described as a small tube, within a larger one, the smaller
extremity of the inner tube projecting beyond that of the outer one.
Deshayes, who describes this genus, expresses a conviction that the
soft parts of the animal must be entirely different from those of the
animal of Dentalium. The genus PHARETRIUM, as described by König in his
"Icones Fossilium Sectiles," is evidently identical with Entalis. It is
placed by him in the family of Pteropoda, but being a fossil shell,
there is some difficulty in finding its place in the system. See
plates, fig. 3.
ENTELLITES. Fischer. A genus composed of species of TEREBRATULA,
SPIRIFER, and PRODUCTUS, Auct. having the hinge large and the umbones
short. ORTHIS? Dalman.
ENTIRE. (Integra.) Not interrupted, not emarginated. The peritrême of a
univalve shell is said to be entire when not interrupted by canals or
by the body whorl. _Ex._ Cyclostoma, fig. 304. The palleal impression
is entire, when continued without interruption, or without a sinus.
ENTOMOSTOMATA. Bl. The second family of the order Siphonibranchiata,
Bl. The shells of this family are described as differing but little
from those contained in the family of Siphonostomata of the same
author, both with regard to the soft parts, and their testaceous
covering. This family partly answers to the Purpuriferæ in the system
of Lamarck, and contains the genera Subula, Cerithium, Melanopsis,
Planaxis, Terebra, Eburna, Buccinum, Harpa, Dolium, Cassidaria, Cassis,
Ricinula, Cancellaria, Purpura, Concholepas.
EOLIDES. Montf. A genus of microscopic Foraminifera.
EPIDERMIS. ([Greek: Epi], _epi_, over or upon; [Greek: derma], _derma_,
skin.) The fibrous, horny, external coating of shells, called by the
French, "_Drap marin_," or marine cloth. Lamarck objects to the name
Epidermis because he does not consider the substance as answering to
the cuticle or scarf skin of the human body, but more analogous to the
nails and hair. Gray calls it the PERIOSTRACUM, from the membranous
skin covering the bones of quadrupeds.
EPIPHRAGM. The membranaceous or calcareous substance by which some
species of molluscs close the aperture of the shell, when they retire
within it to hibernate. When the animal wishes to come forth from his
hiding-place, again to breathe the air, the edges of the Epiphragm are
detached by a chemical process, so that it drops off. The name
Hibernaculum has also been given to this covering. It must not be
confounded with the operculum, which is a permanent portion of the
shell, and is used as a door, fitted to the foot of the animal and
moved at will to open or close the aperture of the shell, whereas the
Epiphragm is produced for the occasion from a mucous secretion of the
animal and dissolved at the edges when no longer wanted, when it drops
off.
EPISTYLA. Sw. A subgenus of the genus HELIX. E. conical. Sw. Helix
Epistylium, fig. 281.
EPONIDES. Montf. A genus of microscopic Foraminifera.
EQUILATERAL. (Æquus, equal; latus, side.) Equal-sided. A term applied
to bivalve shells, when a line drawn down perpendicularly from the apex
would divide the shell into two equal parts. _Ex._ Pectunculus pilosus,
fig. 134.
EQUIVALVE. (Æquus, equal; _valva_, a valve.) A term applied to a
bivalve shell when the valves are equal to each other in dimensions.
ERATO. Risso. _Fam._ Convolutæ, Lam.--_Descr._ Ovate, more or less
angulated, smooth or granulated, with a dorsal scar; spire short;
aperture large, angulated, emarginated; columella slightly crenated;
outer lip reflected, denticulated on the inner edge. Suture of the
whorls covered with enamel.--_Obs._ This genus of shells resembles
Marginella in form, but has no folds on the columella. Having a scar or
groove down the back it may be considered intermediate between
Marginella and Cypræa. Fig. 454, E. Maugeriæ. In the Author's
Conchological Illustrations, seven species are enumerated and figured.
ERUCA. Sw. A subgenus of Clausilia. Sw. Malac. p. 334.
ERVILIA. Turt. A genus described as "oval, equivalve, equilateral,
closed. Hinge with a single erect tooth closing between two small
diverging ones in the opposite valve: lateral teeth none. Ligament
internal. E. nitens. Turt. Mya. nitens, Auct."
ERYCINA. Lam. _Fam._ Mactracea, Lam. Conchacea, Bl.--_Descr._ Ovate or
triangular, transverse, equivalve, inequilateral, smooth; hinge with a
ligamentary pit, two diverging cardinal and two lateral teeth in each
valve; muscular impressions two in each valve; palleal impressions
sinuated. East and West Indies and Mediterranean.--_Obs._ This genus is
distinguished from _Mactra_ and _Lutraria_ by the cardinal teeth being
placed one on each side of the ligamentiferous pit; whereas in the last
named genera they are both placed on the anterior side. Fig. 86, E.
Plebeja.
ERYTHRÆA. The ancient name for CYPRÆA.
ESCUTCHEON. The impression on the posterior dorsal margin of some
bivalve shells. That on the anterior margin is named the lunule. The
escutcheon is pointed out by the letter _e_ in some of the figures of
Cythereæ. Fig. 117, _a. b. c._
ETHERIA. Lam. (_Æther_, air.) Fam. Chamacea, Lam. and Bl.--_Descr._
Irregular, inequivalve, inequilateral, foliaceous, pearly within,
covered by an olive green epidermis without; hinge callous, undulated,
destitute of teeth; ligament partly external, partly internal, passing
through the hinge on a somewhat raised, callous area in the lower
valve. Muscular impressions elongated, two in each valve, united by a
slender palleal impression. Rivers of Africa.--_Obs._ The irregular,
unequal air-bubbles of the inner surface, whence this genus derives its
name, are very brilliant in some species, and atone, in some measure,
for the rugged ugliness of the exterior. In its irregular form,
foliated structure, and toothless hinge, it resembles OSTREA, from
which it differs in having two muscular impressions. Fig. 155, E.
semilunata.
EULIMA. Risso. _Fam._ Scalariens, Lam.--_Descr._ Elongated, smooth,
pyramidal; spire long, composed of numerous whorls; apex acute,
slightly tortuous; aperture oval, rounded anteriorly, acute at the
posterior union with the body whorl; outer lip slightly thickened;
columella smooth. Fig. 347, E. labiosa, fig. 348, E. splendidula. A
complete illustrated monograph of this genus of pretty shining little
shells, consisting of 15 known species, is given in parts 52 and 53 of
the Conchological Illustrations by the author.
EUOMPHALUS. Sow. _Fam._ Scalariens, Lam.--_Descr._ Orbicular,
planorbular spire, with three or four volutions, imbricated above;
smooth below; aperture of a round polygonal form; umbilicus large,
penetrating to the apex of the shell.--_Obs._ This genus of fossils
very nearly resembles Delphinula. The main difference appears to be
that the whorls do not increase so rapidly in size in the former as in
the latter. Fossil, in the Carboniferous Limestone. Fig. 350.
EXOGYRA. Sow. A genus of fossil bivalves, resembling Chama in shape and
Ostræa in structure, having but one muscular impression in each valve.
Fig. 183.
EXSERTED. Standing out, protruding.
EXTERNAL. An external shell is one which contains the animal, and is
not covered by the mantle.
FASCIATED. (_fascia_, a band.) Banded or striped. Ex. Carocolla
marginata, fig. 277.
FASCICULATED. (from fasciculum.) A little bunch of hairs or bristles
against each end of each valve, characterizes some species of the genus
Chiton, which are termed fasciculated species.
FASCIOLARIA. Lam. _Fam._ Canalifera, Lam. Siphonostomata, Bl.--_Descr._
Elongated, fusiform, ventricose; spire conical, consisting of few
rounded or angulated whorls; aperture wide, terminating in a long
straight open canal: columella lip with several oblique folds, the
lower of which is larger than the rest; operculum horny,
pyriform.--_Obs._ This genus is known from Fusus by the folds on the
columella; from Turbinella, by their obliquity and the last being
larger than the rest. Fig. 386, F. Trapezium. East and West Indies and
Australia.
FAUNUS. Montf. MELANOPSIS, Auct.
FERRUGINEOUS. Of an iron rust colour.
FERUSSINA. Grateloup. STROPHOSTOMA, Deshayes.
FIBROUS. A shell is said to be of a fibrous structure when a fracture
would present a series of perpendicular fibres, as Pinna.
FICULA. Sw. A generic group of shells, consisting of those species of
PYRULA, Auct. which have the true pear-shaped character. Fig. 390, P.
Ficus. Sowerby confines the name Pyrula to these species.
FIMBRIA. Megerle. CORBIS, Lam.
FIMBRIATED. Fringed; as Murex fimbriatus, a delicate white species,
with broad fringed varices.
FISSURE. (_Fissura_, a slit.) A slit or cut, a narrow perforation, as
in Emarginula and Fissurella.
FISSURELLA. Brug. (_Fissura_, a fissure.) _Fam._ Calyptracia, Lam.
Branchifera, Bl.--_Descr._ Patelliform, oval or oblong, radiated; apex
anterior, perforated.--_Obs._ The Fissurellæ are known from Patellæ by
the perforation in the apex. Fig. 245. The catalogue published by the
author in the Conchological Illustrations, enumerates 68 species.
FISTULANA. Lam. (_Fistula_, a pipe.) _Fam._ Tubicolæ, Lam. Adesmacea,
Bl.--_Descr._ A transversely elongated, equivalve, inequilateral
bivalve, enclosed by a septum within the widest, closed extremity of a
straight calcareous tube. Fistulana is known from Gastrochæna by the
straightness of the tubes, and the oblong state of the valves. Fig. 54,
Fistulana Clava.
FLEXUOUS. Having windings or bendings. _Ex._ The Tellinæ are known by
the twist or flexuosity in the posterior ventral margin of the shell.
FLORILLUS. Montf. A genus of microscopic Foraminifera.
FLUVIATILE. (Fluviatilis.) Belonging to a river or running stream.
_Ex._ Limnæa fluviatilis.
FLUVIATILE CONCHACEA. See CONCHACEA.
FOLIATED, or FOLIACEOUS. (From _folium_, a leaf.) When the edges of the
successive layers of which a shell is composed are not compacted but
placed apart from each other, projecting like tiles, the shell is said
to be of a foliated structure. The common Oyster, fig. 180, presents a
familiar example.
FORAMINIFERA. D'Orb. (_Foramen_, a hole or pit.) An order established
for minute many chambered internal shells, which have no open chamber
beyond the last partition. Lamarck, D'Orbigny, and other writers have
placed them among the Cephalopoda in their systems, but Du Jardin, on
comparing the fossils with some recent species of the same class,
arrived at the conclusion, now generally adopted, that they constitute
a distinct class, much lower in degree of organization than even the
Radiata. Not recognizing these microscopic bodies as shells, properly
so called, but considering them sufficiently numerous and interesting
to form a distinct branch of study, I do not think it desirable to
describe the genera, or to present any arrangement of them in this
work.
FORNICATED. Arched or vaulted, as the exfoliations on the costæ of
Tridacna Elongata, fig. 157.
FOSSIL SHELL. A shell is considered to be in a fossil state when, the
soft parts having ceased to exist, it is deprived of all its animal
juices, has lost all, or nearly all its natural colour, and is thus
changed in its chemical composition, when little or nothing is left but
a mere bone, which is embedded in a sedimentary deposit. In this state,
it is fragile, prehensile to the tongue, and either destitute of colour
or tinged with the diluted mineral matters which pervade the stratum in
which it lies. In some cases, the mineral composition of the shell is
so completely changed as no longer to present its proper structure,
consisting of successive oblique layers of shelly matter; but is
altered into a fibrous structure, composed of rhomboidal particles. An
example of this will be found in the Belemnites, which if broken, shew
the perpendicular fibres. In other cases, the matter which has entered
and filled up the cavities of the shell has become silicified, or
changed into flint, and the shell itself has been decomposed and fallen
off, so as to leave nothing but an external or internal cast of its
form, in flint. This is called a Conchyliomorphite by continental
writers. Some of the most important of Geological data are obtained by
a minute comparison of fossil shells, found in various beds, with
recent ones presenting the nearest resemblance to them. Some species of
fossil shells are considered as identical with recent species. And many
Geologists seek to fix the chronology of the different strata by the
number of species which they inclose bearing a resemblance to the
recent species. Indeed, all who would study Geology with success, will
find it indispensably necessary to obtain a thorough knowledge of
Conchology.
FRAGELLA. Sw. A sub-genus of Monodonta, corresponding with the genus
Clanculus, Montf. consisting of M. Pharaonis (fig. 361), and similar
species. Sw. p. 352.
FRAGILE. (_Fragilis._) Tender, easily broken.
FREE SHELL. One that is not attached.
FREE VALVE. In attached bivalve shells, one only is fixed; the other is
then _free_, as far as to the action of opening and shutting.
FRESH-WATER SHELLS, (sometimes described as aquatic) are those which
either inhabit rivers, running pools and ditches, in which case they
are _fluviatile_; or wells and ponds of standing water, &c. Fresh-water
shells are either thin and horny in their texture, as the Limneana of
Lamarck; or are covered with a compact, smooth, horny epidermis. They
are generally simple in form, subject to corrosion where the epidermis
is wounded or broken, and are circumscribed with regard to the classes
and genera to which they belong. The family of Nayades includes nearly
all the fresh-water bivalves; and the Melaniana and Limneana are the
principal among univalves.
FRONDICULARIA. Defr. A genus of microscopic Foraminifera.
FRONT. The surface of a shell on which the aperture appears.
FULCRUM. That part of a shell on which any other part rests or turns.
The term is applied more particularly to the tumid part in the hinge of
bivalve shells on which the ligament is fixed.
FULGUR. Montf. PYRULA perversa, Auct. and such other species as have an
angulated spire. Fig. 388.
FUSIFORM. (_Fusus_, a spindle.) Shaped like a spindle, swelling in the
centre and tapering at the extremities. _Ex._ Fusus, fig. 387.
FUSUS. Brug. (A spindle.) _Fam._ Canalifera, Lam. Siphonostomata,
Bl.--_Descr._ Fusiform, turrited, with many rounded whorls; aperture
generally oval, terminating in a long straight canal; operculum horny,
pyriform.--_Obs._ The Fusi are subject to considerable variations in
form. The recent species are numerous and do not appear to be confined
to any climate. The fossil species are also numerous, chiefly abounding
in the tertiary formations. The recent species are mostly tropical.
Fig. 387, F. Colus.
GALATHÆA. Brug. POTAMOPHILA, Sow. MEGADESMA, Bowd.
GALEA. Klein. PURPURA, Auct.
GALEOLARIA. Lam. (From Galea, a helmet or crest.) A genus composed of
species of SERPULA, Auct. Distinguished as being fixed by the side of
the shell, and having the anterior extremity erect, the aperture
terminating in a tongue-shaped projection.--_Obs._ This genus is said
by Lamarck to resemble Vermilia in other respects, but to differ in
having the anterior part raised. Fig. 6, G. decumbens. Africa and
Australia.