_U. bigbyensis_ Lea, ’41. _U. estabrookianus_ Lea, ’45. _U. fassinans_
Lea, ’68. _Pleurobema fassinans rhomboidea_ Simpson, ’00.
The most frequent form is _fassinans rhomboidea_ (topotypes examined),
with rays poorly developed. _U. bigbyensis_ has more distinct rays; _U.
estabrookianus_ (topotypes examined) is an old, overgrown form, without
rays; _U. fassinans_ is founded upon an individual (type examined, also
topotypes), which is exceptionally elongated, without rays.
3. FUSCONAIA BARNESIANA TUMESCENS (Lea) 1845.
_U. tumescens_ Lea, ’45. _U. crudus_ Lea, ’71. _U. radiosus_ Lea, ’71.
_U. tumescens_ is the most typical form, greatly swollen, with more or
less developed rays; _U. radiosus_ (type and topotypes examined) is less
swollen, but for the rest like _tumescens_; _U. crudus_ (topotypes
examined) lacks rays, and has much eroded beaks, but stands close to
_radiosus_.
The mutual relations of these forms may be understood by the help of the
following key. Only the three largest divisions are to be regarded as
varieties, in the other forms the characters are merely individual,
although specimens representing only one (or a few) of these “forms”
often prevail at a given locality.
a_{1}. Flat, compressed, dia. of shell less than 40 per cent of the
length (var. _bigbyensis_).
b_{1}. No rays, or rays obscure, color of epidermis brown, dark.
c_{1}. Rhomboid in shape.
d_{1}. Large. _Estabrookianus._
d_{2}. Smaller. _Fassinans rhomboidea._
c_{2}. More ovate, tapering behind. _Fassinans._
b_{2}. Rays distinct, well developed over most of the disk. Ground
color of epidermis lighter. _Bigbyensis._
a_{2}. Moderately convex, dia. 40‒49 per cent of length. _Barnesiana
typica._
b_{1}. Beaks not elevated, shape trapezoidal, rhomboid, or subovate.
c_{1}. Dia. about 41 or 42 per cent; size small.
d_{1}. Shape somewhat elongate (trapezoidal); rays obscure.
_Barnesianus._
d_{2}. Shape shorter (rhomboidal).
e_{1}. Rays obscure. _Lenticularis._
e_{2}. Rays present, color of epidermis lighter.
f_{1}. Rays few. _Meredithi._
f_{2}. Rays numerous. _Pudicus._
c_{2}. Dia. about 45 per cent; larger. Shape subovate. Rays obscure.
_Tellicoensis._
b_{2}. Beaks more elevated, shape subtriangular. Dia. 46 per cent,
with rather distinct rays. _Lyoni._
a_{3}. Much swollen, dia. over 50 per cent. Beaks elevated. (var.
_Tumescens_).
b_{1}. Without rays. Dia. 51 per cent. Beaks much eroded. _Crudus._
b_{2}. With rays. Dia. about 56 per cent or more.
c_{1}. Dia. about 56 per cent. _Radiosus._
c_{2}. Dia. about 64 per cent. _Tumescens._
As to the geographical distribution, it should be briefly stated that
the swollen forms (a_{3}) inhabit the largest rivers; the compressed
forms (a_{1}) are found in the headwaters, and the intermediate forms
(a_{2}) belong to the streams of moderate size. Intergrades are
frequent.
ANATOMY.[7]
All these shells have the same, and an extremely characteristic and
unique structure of the soft parts, so that there is not the slightest
question that they belong together. I have examined the soft parts of
some 200 specimens in the field, and over three dozens have been
preserved in alcohol, and have been examined at leisure in the
laboratory. They include representatives of the three main varieties,
and of practically all of the individual variations.
_Gravid females_ have been found on the following dates: May 11, ’13;
May 15, ’13; May 16, ’13; May 20, ’13; May 20, ’14; May 22, ’14; May 25,
’14; July 5, ’13; July 9, ’13; July 10, ’13; July 13, ’13; July 14, ’13.
_Glochidia_ have been observed on May 20, ’14 (immature), and July 14,
’13. Thus this species evidently is a summer breeder (tachytictic).
The soft parts are those of the genus _Fusconaia_: the _supraanal_ is
separated from the _anal_ by a very short mantle-connection, which is
absent (or torn?) in rare cases. Inner lamina of inner gills free from
abdominal sac. All four gills are marsupial. Placentae well developed
and subcylindrical.
_Branchial opening_ with well developed papillae, _anal_ with distinct,
but small papillae. _Palpi_ subfalciform, posterior margins connected at
base only.
While thus the _Fusconaia_ structure is typically developed, this
species is quite unique in its color. This concerns chiefly the color of
the gonads, eggs, and placentae.
The soft parts are often uniformly pale, whitish, but may shade to
orange, and the orange is most prominent on foot, adductors, and
mantle-margin; but the paler tints prevail, and often the orange is
replaced by yellowish or brown. The gills are pale, but are generally
suffused with blackish. The gonads are brown to red, mostly of a
peculiar dull lavender color in the female, and the latter color, or
purplish brown, is the prevailing color of the eggs and placentae. The
charged gills become thus rather dark purple, or purple-brown, shading
sometimes to dull red or blackish, in other cases to brownish, brownish
pink, brick-red, or even pale brown. These are very peculiar tints, by
which this species is easily recognized in the field: four marsupial
gills of this blackish-purple color are not known in any other Nayad.
_Glochidia_ have been found only in specimens belonging to the
headwaters variety (_barnesiana bigbyensis_). They are subelliptical,
slightly higher than long, L. 0.15, H. 0.16 mm.
Although a true _Fusconaia_, this species (or group of forms) stands
isolated within the genus, in characters of the shell as well as in the
soft parts. It differs from the species of the _subrotunda_-group (ind.
_ebena_, _pilaris_ etc.) very markedly by its smaller size and by the
very shallow beak cavities. The forms of the _undulata_-group (incl.
_flava_, and the _cuneolus_- and _cor_forms) have generally also
somewhat deeper beak cavities, and the shell has a more or less distinct
posterior ridge, with a flattening or a shallow groove in front of it,
characters which are missing in the _barnesiana_-group. As has been
pointed out, in the latter group, the color of eggs and placentae is
remarkable: in all other forms of _Fusconaia_, this varies from white to
bright red.
I introduce here another species, in order to show that
the _barnesiana_-type is also represented outside of the
Cumberland-Tennessee drainage, namely in the Ozarks.
FUSCONAIA OZARKENSIS (Call) 1887.
_F. ozarkensis_ Call, Pr. U. S. Mus. 10, ’87, p. 499, pl. 27. Tr. St.
Louis Ac. 7, ’95, p. 33, pl. 18. _Lampsilis ozarkensis_ Meek & Clark,
Bur. Fisher. Doc. no. 759, ’12, p. 18. _Pleurobema utterbacki_ Frierson,
in: Utterback, Naiad. Missouri (Amer. Midland Natural 4, 1916, p. 86,
pl. 5, pl. 20, f. 63).
I have specimens from James River, Galena Stone Co., Mo., and White
River, Cotter and Norfolk, Baxter Co., Ark., donated by L. S. Frierson
and collected by A. A. Hinkley on July 30 and Aug. 2 and 5, ’14, A
number of specimens (8) were preserved in alcohol, coll. July 30 and Aug
2, which all were gravid females, and one of each date had glochidia.
This marks probably the end of the breeding season, and the species is
tachytictic.
There is some confusion with regard to this species. After the first
description by Call, it has not again been recorded, except by Meek and
Clark, and I believe, the identification of these authors (supported by
B. Walker) is correct. But I think that other authors have seen this
form, but have not recognized it, and, for instance, Simpson’s
_pannosus_ and _subellipticus_ (regarded as varieties of _Pleurobema
argenteum_ and _breve_ respectively) are also this. Frierson’s
_utterbacki_ is surely this, since my specimens were thus labeled by
Frierson.
Walker, Frierson, and Simpson (in part) believe this to be a
_Pleurobema_, and not a _Lampsilis_ (see also Simpson, ’00, p. 557, and
’14, p. 131), and this comes nearest to the truth, in fact, it is the
most plausible assumption to be made from the study of the shell alone.
The shell “resembles a very elongated _Quadrula coccinea_,” according to
Meek and Clark, and the comparison with _Pleurobema argenteum_ and
_breve_ (which, by the way, are synonyms), made by Simpson, is
significant. We must keep in mind that Call’s fig. 4 represents the
normal shape of the shell, while his fig. 1 is rather abnormal, and
possibly does not belong here at all. These two figures by no means
represent the female and male, as Call believes.
The investigation of the soft parts has shown that this actually is a
_Fusconaia_. Corresponding, both in soft parts and shell, to the
_barnesiana_-type of the upper Tennessee region. _F. ozarkensis_ differs
from _barnesiana_ by the more elongated (subtrapezoidal) outline of the
shell, more anterior beaks, and the weak development of the rays, which
are faint at the best, and often entirely absent. A swollen form of it
is not known to me, but specimens from White River are slightly more
convex than those from James River (farther up). Also Utterback’s
quotation of Frierson (p. 87, footnote) make it probable that there are
differences in obesity.
ANATOMY.
_Supraanal_ opening probably separated from the _anal_ by a short
mantle-connection, but in all my specimens this is torn by rough
handling. Inner lamina of inner gills free from abdominal sac. All four
gills marsupial in the female. _Placentae_ well developed and
_subcylindrical_.
Anal opening with small papillae, branchial opening with well developed
papillae. _Palpi_ as usual, their posterior margins connected for about
one third of their length or less.
As to the color of the soft parts, which is so characteristic in
_barnesiana_, not much can be said, since my material has been too long
in alcohol. But in most of my specimens the gills are yet distinctly
suffused with black. The placentae have been rendered whitish, but here
and there traces of a dark stain are preserved (which is disappearing
gradually). It is quite possible that the color of the placentae
originally was similar to that of _barnesiana_.
The _glochidia_ are subelliptical, slightly higher than long; L. O. 15,
B. O. 18, thus agreeing with those of _F. barnesiana_.
NOTE ON THE RELATION OF SNAIL FAUNA TO FLOODS.
BY A. RICHARDS.
During the years 1911 to 1916, while the writer was a member of the
faculty of the University of Texas, a series of incidental observations
on the snail fauna of Waller Creek was made. These observations have now
come to an end due to the change of residence of the observer. It seems
not unwise, therefore, to publish a short note on the subject in the
hope that the facts recorded, although fragmentary, may have a bearing
on the work of some other follower of snail life.
Waller Creek is a small stream near the University of Texas at Austin.
It is some four miles in length and empties into the Colorado River at a
distance of perhaps two miles below the University. That portion of the
stream close to the University between Fifteenth and Twenty-seventh
Streets, was most closely observed, but data was also collected from the
region below. During the hot months, from about July 1st to October 1st
usually, the stream is dry, or water is to be found only in an
occasional pool; during the rest of the year the water flows to a depth
of a few inches. The bed is scoured out of limestone (Austin Chalk) and
has for much of its length a solid flat rock bottom. The banks of the
creek have in general a gradual slope. In time of flood and during heavy
rains, this stream rises very rapidly and quickly becomes bank-full, so
that the water rushes down in a torrent, the roar of which may at times
be heard for a distance of some blocks. The fall of the creek is
considerable, being about 75 feet in two miles from Twenty-seventh
Street to the Colorado, and this fall in connection with the shape of
the bed gives to the current in times of flood a tremendous force.
During the first two years of this observation, 1912‒1913, the snail
population of the creek in its middle stretches was dense. There were in
particular two species very thickly represented, _Planorbis lentus_ and
_Physa halei_. So numerous were they that one could in a few moments
within a very few feet gather a pint of either kind. Wherever a little
ripple or a tiny waterfall occurred were many snails oriented in
relation to the current, their heads pointing into it. Elsewhere in the
more quiet water they were also to be found, but in less numbers. These
conditions obtained especially in the early spring; as the breeding
season, which in that latitude extends over half the year, passes by,
the snails of course become much less numerous.
It is to be noted that previous to the time when the snails had become
so abundant, there had been no heavy rains of sufficient importance to
be recorded since 1908. Excessive rains occurred in May 1908, November
and May 1907, June and March 1905, May and April 1904, July and February
1903, July and November 1902. There was a very severe flood in the creek
in April 1900. It will be seen that between the time when my
observations began and the last excessive rain considerable time had
elapsed and the snails had had the opportunity to reinstate themselves
in the creek, assuming that they had suffered in those floods as they
have done in the later ones.
In the fall of 1913 there were two floods of unusual proportions in the
creek. In October it rose very rapidly, but shortly subsided, and in
November, at the time when the entire state was visited by the most
severe flood since 1869, it was again subjected to a very thorough
scouring. Excessive rains fell on several consecutive days, and streams
in the entire Colorado watershed were out of their banks.
After the heavy rains of the earlier part of the month there were
several days upon which the rainfall, while comparatively light, was
sufficient to keep the creek much higher than its normal level. When the
water finally subsided to its normal amount the bed was covered
completely with a layer of detritus and soft green humus and algae from
a half an inch to an inch in thickness. This deposit and the acids
formed from it have been the cause of a much more rapid disintegration
of the limestone than had been the case in the immediately preceding
years. Loose pieces of limestone which were exposed to the action of the
water had in many cases fallen apart by the end of January. Further
rises occurred on April 27 and on May 20th, 1914, but were not
sufficient to remove all of the accumulated layer of detritus.
In January 1914, a search for snails where they had before been numerous
failed to reveal a single specimen of _Planorbis_ and less than half a
dozen _Physa_. Even in the deeper pools they could scarcely be found.
Later in the spring in the lowest part of the stream a number of very
small _Physa_, as well as some clusters of eggs were found. The force of
the current had been so great as to wash the snails down to the river,
and it is possible that the condition of the water due to the
decomposing humus may have affected those which were able to escape the
flood danger. That some of the Physa were left after the flood may be
attributed to their pointed shape which decreases the amount of force
that the water was able to exert on them as compared with that on the
flat Planorbis shells. Except as noted above in April and May 1914, the
conditions in the creek remained as normal.
In January 1915, Physa has again made its appearance in the middle parts
of the stream, although in small numbers only. Diligent search, however,
failed to reveal a single Planorbis. The snails which were present were
found only under fair-sized rocks where they were well protected; they
did not occur out in the open stream as had been the case when the creek
was more densely populated with snails.
In April 1915, on the 22d and 24th, Waller Creek was swept by three
scouring floods which devastated the entire bottoms. The water rose
higher during the night than it had at any time since 1886; bridges were
washed away and much damage done. The bottom of the creek was again
washed clean except under the larger stones and in deep holes in the
bed. Snails were not observed in any numbers following this flood during
the rest of that year. Early in January 1916, however, Physa had again
appeared fairly abundantly where they had formerly been very thick, in
the region just above the University; later in the spring they became
quite numerous here. In January of this year the first Planorbis were
found that had been seen in the creek since the autumn floods of 1913.
Between Fifteenth and Sixteenth Streets in a pocket containing
good-sized stones over which the water flows rather swiftly a number of
specimens were taken, although none were found above or below this
locality. It is noted that below this region the creek is frequently
covered with oily scum and that it receives the refuse from the
adjoining properties. Except after high water which would clean it out,
the creek in this region would hardly be expected to support much snail
life. It must be supposed either that the Planorbis had made their way
up to Sixteenth Street during the short time following the floods before
the water became badly contaminated, or else that in this particular
place a few specimens from the previous years had withstood the floods
and reproduced themselves in sufficient numbers to be noticeable in
January. Of these two suppositions the latter seems much the more
rational.
After the flood of 1915 the water subsided very quickly so that a new
layer of humus and algae was not deposited, but that the bed was again
restored to its former condition of a clean smooth rock bottom. Upon the
return to this condition the snail population increased very rapidly,
and at the time when the last observation was made in the early summer
of 1916, seemed in a fair way to return to the condition of 1912.
It seems to the writer that the slow return of the snails during the
year 1914 was due not only to the repeated rains of the fall and winter
of 1913‒14, but also to the condition of the creek bed at this time.
Although the heavy rains of 1915 were more severe, they were confined to
one month, and the creek bed was left in a very much cleaner condition
than during the preceding year.
The conditions of life which obtain now in Waller Creek are those of a
new life region. This must of necessity be so in an intermittent stream
to a certain extent, but owing to the flood conditions here they are
doubly so.
The chief facts of interest in regard to the habits of snails as shown
by these observations, are these: 1, The snails of both species are to
be found commonly in uncontaminated water which is running at a fairly
rapid rate, and the most common orientation is with the heads pointing
up stream; 2, The snail population in any stream is subject to wide
fluctations depending upon flood conditions; 3, Physa because of its
shape is less affected by floods than Planorbis; 4, The return of the
snail population to a given stream is determined not only by the
frequency and severity of the floods, but also by the condition of the
bottom of the stream after the subsidence of the high water; 5, The
snails thrive best where there is a constantly renewed supply of clean
water which contains little decaying vegetation.
_Wabash College, Crawfordsville, Ind._
WILLIAM BULLOCK CLARK.
Dr. William Bullock Clark, professor of geology in the Johns Hopkins
University, eminent for his contributions to geology, died suddenly from
apoplexy on July 27, at his summer home at North Haven, Maine.
Wm. Bullock Clark was born at Brattleboro, Vermont, December 15, 1860.
Since 1894 he was professor of geology in Johns Hopkins University. In
1896 Professor Clark organized the Maryland Geological Society, and has
been State Geologist since that time. The admirable volumes on
paleontology of Maryland, issued under his direction, are widely used by
conchologists interested in fossil mollusks. This series of reports will
be his enduring memorial. Professor Clark’s chief paleontological
interest was in the _Echinoidea_, upon which he published several
monographs.
PUBLICATIONS RECEIVED.
A MONOGRAPH OF WEST AMERICAN MELANELLID MOLLUSKS. By Paul Bartsch (Proc.
U. S. Nat. Museum, Vol. 53, pp. 295‒356, pls. 34‒39, Aug. 1917). This
completes the discussion of the West American mollusks of the
super-family Pyramidelloideae, comprising the family Pyramidellidae,
which has been previously treated, and the Melanellidae here considered.
The former are readily distinguished by having the “nepionic whorls
sinistral and tilted; the axis of the early whorls usually being at
right angles to that of the succeeding turns, in the first of which the
nuclear whorls are frequently quite strongly imbedded.” In the latter
the early whorls are dextral and never tilted or immersed. A review of
the work done in this group is followed by the descriptions of the
species, including forty-nine new species and one new genus
_Eulimostraca_. The illustrations are excellent.
* * * * *
NEW AND LITTLE KNOWN SPECIES OF SOUTH AMERICAN MUSSELS OF THE GENUS
DIPLODON. By William B. Marshall (Proc. U. S. Nat. Museum, Vol. 53, pp.
381‒388, Pls. 50‒55, August, 1917). Two new species _Diplodon
felipponei_ and _D. fortis_ are described and figured, together with six
species described by Mr. C. T. Simpson in his Descriptive Catalogue of
the Naiades and not previously figured.
* * * * *
NOTES ON THE SHELLS OF THE GENUS EPITONIUM AND ITS ALLIES OF THE PACIFIC
COAST OF AMERICA. By William H. Dall (Proc. U. S. Nat. Museum, Vol. 53,
pp. 471‒488, August, 1917). An interesting account of the various groups
and subgenera is followed by descriptions of forty-two new species.
The name Pictoscala is proposed for a section, type _Scalaria lineata_
Say.
* * * * *
STUDIES ON AUSTRALIAN MOLLUSCA. PT. XIII. By C. Hedley (Proc. Linn. Soc.
New South Wales, 1916, vol. 41, pt. 4, pp. 680‒719, pls. 46‒52, issued
April 4, 1917). The author’s notes under _Tridacna gigantea_ Perry are
of such general interest that we quote them in part. “Under the name of
_Chama gigas_ the father of Natural History seems to have embraced the
whole of the modern genus _Tridacna_. For the name _gigas_, as
restricted to a single species, the candidates are the shell
subsequently named _squamosa_ by Lamarck and a huge species whose valves
in the Ulrica Museum, together weighed 498 pounds.
“After careful examination, Hanley decided that the furbelowed clam,
such as Reeve has figured for _T. squamosa_, ought rightly to bear the
name _gigas_. He based his verdict on the ground that the actual shell
owned by Linné as representing _gigas_, is the Lamarckian _squamosa_,
and that to this apply most of the literary references. Linnean
contemporaries such as Born, Regenfuss and Chemnitz, while making casual
references to the giant, all agree in figuring and describing _squamosa_
as the Linnean _gigas_.
“Discriminating in 1819 between the species his predecessors had
confused, Lamarck unlawfully used the name _gigas_ for the largest form,
while for the Linnean _gigas_ he proposed _squamosa_. Attentive to the
remarks of Hanley, Hidalgo in 1903, renamed the biggest species _T.
lamarcki_. But in 1811, Perry had already used the name _Chama gigantea_
for ‘the largest shell at present known.’ As the young of the giant has
not yet been traced to the adult, it is still possible that _squamosa_
is a juvenile deeper-water form of the large intertidal and abraded
_gigantea_.
“The heaviest known are a pair weighing 550 lbs., which Cuvier and
Lamarck relate were presented by the Venetian Republic to Francis I.
These still exist, their edges bound with brass, as holy-water basins in
the cathedral of St. Sulpice, in Paris.
“The photographs of Saville Kent show the giant clams in their natural
position on the Great Barrier Reef, where they occur free and exposed at
low tide, standing on their umbones, and showing their brightly colored
mantle and so-called eyes as they gape.”