Part 3

There were some soldiers encamped at Digby, and they used to gather _Litorina littorea_ and steam and eat them, without any flavoring. They sometimes ate _Thais lapillus_ also. One day, after a rain, we found two _Helix hortensis_ crawling along the road.

A NEW TYPE OF THE NAYAD-GENUS FUSCONAIA. GROUP OF F. BARNESIANA LEA.

BY A. E. ORTMANN.

During the study of the nayad-fauna of the upper Tennessee, the present writer found that there exists, in this region, a peculiar type of shells, belonging to the genus _Fusconaia_, the various forms of which have been described previously under a great number of specific names, which, however, seem to belong all to one species. In addition, among material received from L. S. Frierson from the Ozark Mountains, a form was discovered which presented the same structure.

The oldest name for the upper Tennessee form is _Unio barnesianus_ Lea. A more detailed account of its various phases is to be given elsewhere, and it suffices here to mention only those forms which belong here. According to obesity, I distinguish three local, or ecological races:

1. FUSCONAIA BARNESIANA (Lea) 1838.

_U. barnesianus_ Lea, ’38. _U. meredithi_ Lea, ’58. _U. pudicus_ Lea, ’60. _U. Lyoni_ Lea, ’65. _U. tellicoensis_ Lea, ’72. _U. lenticularis_ Lea, ’72.

As the normal (most abundant) forms we may regard _U. meredithi_, _pudicus_ and _lenticularis_, which differ from each other only in the development of the rays (topotypes examined). _U. barnesianus_ is a slightly more elongated individual, with poorly developed rays. _U. tellicoensis_ (topotypes examined) is a _lenticularis_ slightly more swollen; and _U. Lyoni_ forms the transition toward var. _tumescens_, having a little more elevated beaks, greater obesity, and rather distinct rays.

2. FUSCONAIA BARNESIANA BIGBYENSIS (Lea) 1841.

_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.

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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.

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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.

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