590.5 FI V.28-Z9 The person charging this material is re- sponsible for its return to the library from which it was withdrawn on or before the Latest Date stamped below. Theft, mutilation, and underlining of books are reasons for disciplinary action and may result in dismissal from the University. UNIVERSITY OF ILLINOIS LIBRARY AT URBANA-CHAMPAIGN ^N^tjfl? ^^""""^W&fc F L161 — O-1096 THE LIBRARY Of iHt JUN251943 ZOOLOGICAL SERIES OF FIELD MUSEUM OF NATURAL HISTORY Volume 29 CHICAGO, JUNE 10, 1943 No. 1 MALACOLOGICAL NOTES— III BY FRITZ HAAS CURATOR OF LOWER INVERTEBRATES Field studies on mollusks and other marine invertebrates of the California coast, in the interest of Field Museum's Division of Lower Invertebrates, were undertaken in April and May of 1941. The observations and collections made in such a short time would have been impossible without the accommodations that the Scripps Institution of Oceanography at La Jolla and the Hopkins Marine Station at Pacific Grove kindly put at my disposition; I was further helped by the active aid of West Coast biologists, especially Miss Myra Keen of Stanford University, Dr. Joshua Baily of San Diego, and Mr. Paul S. Barnhart, Scripps Institution, La Jolla. Certain of the observations made, with the descriptions of two new species, are here reported, together with notes accumulated during my curatorial work at the Museum. I am indebted to Mr. Percy S. Barnhart, of the Scripps Insti- tution, for the new figure of the Diplodonta "nest" that had previously been figured by Johnson and Snook, and also for the figure of the shell of a Diplodonta within the shell of a Callithaca. These are from the Baker- Kelsey Collection. . The San Diego Natural History Museum has kindly supplied two additional figures of Diplodonta nests. I am obliged to Mr. E. P. Chace, of San Pedro, California, who has communicated his observations of the nest-building habits of the Diplodonta to me; my data agree closely with his. The figure of Cooperella, supplied through the courtesy of Miss Myra Keen, Stanford University, is from a shell collected by Mr. and Mrs. T. S. Oldroyd, Stanford University Paleontological Type Collection No. 6982. TWO NEW SPECIES OF MINUTE CALIFORNIA MARINE SHELLS While a guest of the Hopkins Marine Station at Pacific Grove, California, I engaged in straining sand from a tidepool at Point No. 529 1 2 FIELD MUSEUM OF NATURAL HISTORY— ZOOLOGY, VOL. 29 Pinos, Monterey Peninsula. Some apparently undescribed species were found among many other minute but well-known species. The drawings accompanying the descriptions were made by Mr. John Janecek, Staff Illustrator. Alvania (Willetia) microglypta sp. nov. Fig. 1, a, b, c. Type from Point Pinos, Monterey Peninsula, California; washed from sand in a tide-pool. No. 17028 Field Museum of Natural History. Collected May 19, 1941, by Fritz Haas. Diagnosis. — A very minute species of the rissoid genus Alvania, subgenus Willetia, characterized by its extreme smallness, by a wide, subglobular nucleus of one and one-half whorls, by a solid shell strongly spirally keeled and by having only the slightest indications of intersecting axial sculpture. Comparisons. — The new form cannot be easily compared to any other known species, since it combines features thought to be characteristic of the subgenus Willetia with features to be found in other West Coast species, e.g. in A. bakeri Bartsch; these points will be discussed below. Description of type. — Shell elongate, conic, creamy white, solid, minute, with four and one-half rather rapidly increasing whorls. Nuclear whorls about one and one-half, voluminous, globular, smooth (fig. 1, c), with the apex sunk below the level of the last half. Post- nuclear whorls three, spirally keeled, separated by a distinct, though by no means very deep suture. Three rather obtuse keels are present on the first post-nuclear whorl, which become more defined on the second whorl, and which assume almost fantastic features on the last post-nuclear whorl, where nodular excrescences are developing on them and where secondary keels intercalate between the original ones or originate below the lowest one. The whorls are rather slender, not swollen, distinctly shouldered, the upper keel forming the angle of the shoulder. Down to the first post-nuclear whorl there is no trace of axial sculpture, but, starting on the second, axial grooves are seen which regularly intersect the space between the suture and the upper keel, carving this into low ridges and furrows of about equal length; the furrows correspond to the axial grooves of the space above the keel. The middle and the lower keels on the second post- nuclear whorl show only indistinct traces of such crossing of an axial sculpture. Finally, on the last post-nuclear whorl, the cutting of the keels into knobs is not traceable to axial sculpture, but has 1943 MALACOLOGICAL NOTES— HAAS become quite irregular; while the marginal knobs of the middle and the lower keels are moderately small and homogeneous, those on the upper keel — by far the thickest of the three — are irregular as to shape and size (fig. 1, a, 6). In an analogous way the space between FIG. 1. Alvania (Willetia) microglypta sp. nov. Field Mus. No. 17028. a, from front; X 50. 6, from back; X 50. c, from top; X 75. the upper keel and the suture is irregularly beset with nodules, the furrows between which correspond to those dividing the knobs of the upper keel. The aperture is oval, doubly lipped, showing the external spiral sculpture weakly within ; the inner lip is thin, smooth, much appressed, and the outer one is thicker, showing the keels at its outer margin. No umbilical chink is discernible. Base of the shell rather flat, smooth, and shiny. Measurements. — Height 0.97 mm., width 0.6 mm., height of aperture 0.41 mm. 4 FIELD MUSEUM OF NATURAL HISTORY— ZOOLOGY, VOL. 29 Remarks. — Only a single specimen of this form was found, and this is somewhat abnormal. Figure 1, a, plainly shows that the uninjured shell must have had about another one- half whorl, so that the total number of whorls amounted to five and one-half; after an injury of some kind, the snail rebuilt the aperture of its shell one-half whorl back from its original position. The keel seen in figure 1, a, left of the aperture, is the rest of the lost half whorl, and beneath it a coat of shiny enamel covers the surface of the shell, corresponding to the smooth original inner sur- face of the lost aperture; this coat of whitish enamel is truncated at the right lower extremity, perhaps covering up the umbilical chink so that no trace of it can be seen in the present specimen. Except for these apertural features, the shell is intact, and its most distinc- tive characters lie in the character of the whorls of the spire. It is probable that the description of the aperture, as given here, will have to be modified. Discussion. — The new species described does not exactly match the definition of the West Coast subgenus Willetia. None of the species of Alvania referred to this subgenus shows the broad, globular nucleus and the preponderant spiral sculpture by which microglypta is characterized. It shares these features with some other West Coast alvanias which form a group with A. castanella Ball or A. bakeri Bartsch, but its sculpture is much heavier than that of this group of species, and its lip is much more developed ; typical species of Willetia, on the other hand, often show such strong spiral ribs and such a broad, even double lip of the aperture. Thus Alvania microglypta is intermediate between these apparently well-dis- tinguished groups, and the original definition of the subgenus Willetia may have to be correspondingly modified. My reference is therefore tentative. Chrysallida (Chrysallida) ornatissima sp. nov. Fig. 2, a, b, c. Type from Point Pinos, Monterey Peninsula, California; washed from sand in a tide-pool. No. 17029 Field Museum of Natural History. Collected May 19, 1941, by Fritz Haas. Diagnosis. — A medium-sized species of the typical subgenus of the pyramidellid genus Chrysallida, characterized by a slender conic shell, an upper constriction of the whorls, and a peculiar pattern of shell sculpture. Comparisons. — The presence of only three keels on the nuclear whorls suggests a closer relation to species like C. oregonensis Ball 1943 MALACOLOGICAL NOTES— HAAS and Bartsch, but the sculptural pattern of the post-nuclear whorls is quite different from that present in the group mentioned. It closely resembles the pattern seen in species like C. oldroydi Dall and Bartsch, but these differ in having five keels developed on their FIG. 2. Chrysallida (Chrysallida) ornatissima sp. nov. Field Mus. No. 17029. a, from front; X 25. b, from back; X 25. c, from top; X 50. nuclear whorls. The classification of the species of Chrysallida is still rather artificial, being based on unstable characters, such as the mutual relation of spiral or axial sculptural elements, and the preponderance of one or the other, so that the relation of the new form with any of the many congeneric species can not yet be stated. Description of type. — Shell elongate-conic, slender, shiny white, composed of five and one-half whorls which increase gradually. 6 FIELD MUSEUM OF NATURAL HISTORY— ZOOLOGY, VOL. 29 Nuclear whorls one and one-half, with three keels, the upper of which forms a sharp edge (fig. 2, c); the first half of the nuclear whorls is immersed (fig. 2, 6). The four post-nuclear whorls are a little inflated, the two upper ones with almost straight sides, the two lower ones with rounded sides. They are separated by a deeply incised suture. The upper part of every post-nuclear whorl shows a narrow but decided and almost concave constriction. The shell is highly ornamented by a sculpture in which axial and spiral ele- ments are almost equal; only on the base of the last whorl does the spiral element preponderate. There are three spiral cords on the first and on the second post-nuclear whorls, four on the third, and five on the fourth, while the base of the shell shows about seven. All these cords are separated by sharply incised furrows about one- half as wide as the cords themselves; on the base of the shell only, these incised lines are much narrower in proportion to the cords. This system of revolving cords is crossed by axial furrows approximately as wide as the incised spiral furrows, but not as deep as these; this means that the points of crossing of spiral cords and axial furrows are at a higher level than the bottom of the incised lines. The consequence of this intersection of both spiral and axial elements is a meshwork presenting the edges of the cords cut into almost square, but obtuse- angled, raised knobs. The lower cords of every whorl are less heavily carved than the upper ones; thus the fourth on the third whorl and the fifth on the fourth whorl are practically intact and have only a somewhat wavy outline, while the cords on the base exhibit almost no intersecting furrows. The aperture of the shell is comparatively small, oval, and simple; its right upper margin, close to the insertion, is somewhat damaged in the type. In the interior of the aperture, the external shell sculpture is somewhat visible. The base of the aperture is decidedly effuse; its left margin is so closely appressed to the base of the shell that no trace of a secondary umbilical chink can be seen. The columella presents a very faint, hardly visible fold. Measurements. — Height 2.7 mm., width 1.25 mm., height of aperture 1 mm. Notes on the paratype. — No. 17030 Field Museum of Natural History. Same locality, same date and same collector as the type. Its measurements are height 2.9 mm., width 1.3 mm., height of aperture 1.1 mm. The paratype matches the description of the type perfectly, with the exception that, being higher, it has an additional fraction of a whorl (about one-fourth). Its aperture is a little damaged, somewhat more so than in the type. 1943 MALACOLOGICAL NOTES— HAAS 7 Discussion. — The West Coast species of Chrysallida, whose number was fifty when Dall and Bartsch wrote their Monograph of the West American Pyramidellid Mollusks, may be double that number now. The species are generally easily recognized, since the respective sculptural patterns offer distinctive features together with differences in the general shape of the shell. It has not yet been possible to split this mass of species into natural groups, the characters used for specific distinction being, apparently, either un- stable or of only secondary value. The number of keels on the phylogenetically oldest part of the shell, the nuclear whorls, might prove to be a useful means for defining natural groups. In Chrysal- lida ornatissima the pattern of sculpture closely resembles, in a general way, that of C. oregonensis Dall and Bartsch, except that the raised parts in ornatissima are impressed in oregonensis, and vice versa. Three main features characterize ornatissima: the pres- ence of three keels on the nuclear whorls, the slender, constricted shape of the whole shell, and the type of meshwork pattern of the sculpture. No other species of Chrysallida appears to possess this combination, though the separate features, or combinations of two of them, occur in numerous species. THE BORING OF LITHOPHAGA1 At the 1940 meeting of the American Malacological Union at Philadelphia, Dr. B. R. Bales reported on his observations on Florida boring mussels and he touched on the problem as to how a bivalve with as soft and as smooth a shell as Lithophaga could successfully attack hard rock. In this connection, I then could refer to Kiihnelt's (1930) experimental work with Mediterranean lithophagas, in which he proved that the carbonic acid produced by the animal's mantle edges is the solvent agent; this shows that Lithophaga is not a mechanical borer, as are the teredinids and pholadids, but a chemical one. This explanation of its boring powers is, of course, only true in the case of limestone rocks, and all the Lithophaga holes in the Mediterranean and the Florida regions were indeed bored into calcareous rocks. On the California coast, I collected Lithophaga plumula Hanley at La Jolla. To my great astonishment, this species had perforated what seemed to be a coarse sandstone, but how could a siliceous 1 A paper incorporating the following three notes was presented in somewhat condensed form at the Eleventh Annual Meeting of the American Malacological Union at Rockland, Maine, August 27, 1941, and was published, without illus- trations, in the Nautilus, 55, No. 4, pp. 109-113, 1942, and 56, No. 1, pp. 30- 33, 1942. 8 FIELD MUSEUM OF NATURAL HISTORY— ZOOLOGY, VOL. 29 rock be attacked by a chemical borer, with an acid no stronger than carbonic acid? A chemical and petrographical analysis made it clear later that while the rock in question is composed of medium to coarse grains of quartz and feldspar these components are cemented together by calcium carbonate. This accounts for the possibility of its being drilled by Lithophaga. The cementing lime is first dis- solved by the action of the carbonic acid, and the loosened grains of quartz and feldspar are then washed out by the water currents produced by the bivalve. The borehole is constantly lined with a thin layer of amorphous calcium carbonate. The assumption that chemical boring is the only means of attack- ing a rock, even a sandstone like that described, is thus not contra- dicted, and is even further supported. But it utterly fails to explain how Lithophaga can drill holes in argillaceous shale. I found this kind of rock, which does not contain a trace of soluble lime, settled upon and perforated by Lithophaga plumula, both at La Jolla and at Pacific Grove. Chemical boring is completely out of the question in this case; mechanical drilling, by rotation of the shell, cannot be proven and is improbable, since the exterior surface of the Litho- phaga shell does not exhibit any vestige of being worn or ground. As in bore-holes drilled in other kinds of rocks, those in the shale are lined out with amorphous calcium carbonate. The fact that Lithophaga can drill holes in non-calcareous argillaceous rocks is thus established, but it cannot yet be explained in any way. Lithophaga plumula is accompanied, in this shale, both by mechanical borers, such as Venerupis lamellifera, some pholadids and Petricola carditoides, and by a bivalve apparently unfit for boring, Botula calif orniensis, which probably bores by the same unknown means as Lithophaga plumula. PROTECTIVE COVERINGS BUILT BY TWO WEST COAST BIVALVES Very little is known about nest-building habits of bivalves. Textbooks, even the most recent ones, mention only the case of limids, which construct a kind of camouflaged nest from byssus- threads and shell fragments or stones, and that of juvenile mytilids, which occasionally have a similar habit. There are, however, other examples of this habit, as I had the occasion to learn on the Cali- fornia coast, where nest cases built by Diplodonta orbella Gould and by the myid Cooper ella subdiaphana Carpenter are known. Diplodonta orbella is rather common, and almost every shell collector on the West Coast knows that it has the habit of building 1943 MALACOLOGICAL NOTES— HAAS 9 a "nest," as they call the protective covering. Notwithstanding this knowledge, there are scarcely any hints in the literature referring to this nest-building habit. None of the textbooks mention it and only scanty, insufficient remarks in rather obscure places give evidence that the fact has been observed. I tried to trace back the literature on this subject and found, as the oldest quotation, a col- lecting notice of I. M. Shepard (1895) in which Diplodonta orbella is reported to have been collected "with nests"; the way these "nests" are mentioned seems to allude to a matter of common knowledge. Josiah Keep, in the first edition of West Coast FIG. 3. Nest of Diplodonta orbella Gould; Shells (1893), does not X 1. Courtesy Scripps Institution. say a wor(j about the nest of our bivalve; so the first source of concise information on the subject is Dall (1901), who says (p. 795) that "it is the habit of the animal to form a sort of nest of sand and adventitious matter, cemented by mucus, with long tubular openings, the whole of irregular form, but completely concealing the inmate." No picture is given. Josiah Keep, in the later editions of the West Coast Shells (1904, 1911, and 1935 [revised by Dr. Joshua Baily]), repeats this statement in almost identical words, adding the words "for the siphons," so that Ball's original description now reads, "with long tubular openings for the siphons." Charles R. Orcutt's Molluscan World (1915), which contains so many valuable observations on molluscan life, does not mention the Diplodonta nest. The first picture of such a Diplodonta covering appeared in 1927 in Johnson and Snook's Seashore Animals of the Pacific Coast; the text accompanying figure 416, on page 438, states that "this species forms a protecting covering of sand cemented by mucus. The cover- ing has long tube-like extensions in which the siphons lie, so that the mollusk is quite hidden." The second edition of the Seashore Animals of the Pacific Coast (1935) repeats this statement literally. Keen and Frizzell (1939) mention only "nests" in connection with Diplodonta orbella. No further literature on this subject has come to my knowledge. Thus, our knowledge of the Diplodonta nest consists of a rather vague description and of a single picture representing a specimen 10 FIELD MUSEUM OF NATURAL HISTORY— ZOOLOGY, VOL. 29 now in the museum of the Scripps Institution of Oceanography at La Jolla. But what does this picture show? In figure 3, which repre- sents the same specimen, the partly broken covering exhibits two long posterior extensions in which, according to the descriptions given by Keep and by Johnson and Snook, the siphons lie. But this explanation cannot be correct, at least concerning the specimen shown, for a close inspection reveals a third though shorter posterior extension, and no bivalve with three siphons is known! A still FIG. 4. Nest of Diplodonta orbella from Terminal Island, San Pedro, Cali- fornia. San Diego Mus. No. 23852. X 1. Courtesy San Diego Museum. closer inspection of the specimen reveals the fact that the three extensions are not hollow tubes at all, but incrusted stalks of sea- weeds; therefore, they cannot be protective coverings of the siphon. They may be regarded as mooring ropes of the shell-covering, as a kind of protection against the shifting action of the waves. Nests with this structure (fig. 4) constitute the most abundant type; they all exhibit extensions, variable in number and of variable length, which either still contain the stalks of seaweed or are hollow, when their original axis of vegetable matter has become disintegrated. This type of nest is built from a felt-like material containing practically no mineral particles and consisting probably of disintegrated plant fibers, kept together by a cementing secretion of the animal. This type of nest may be found loose in holes and crevices of rocks or in empty bivalve shells in which they practically fill out the whole space between the living Diplodonta and the dead shell used as a shelter (fig. 5). In all the cases which came under my observation, the Diplodonta covering of this type seems to consist of two halves corresponding 1943 MALACOLOGICAL NOTES— HAAS 11 to the two valves of the shell, opening at the ventral side and united at the dorsal side of the animal. Besides the type of Diplodonta nest just described, a rarer one may be found which corresponds more closely to the descriptions cited. Figure 6 shows a specimen of Diplodonta orbella in a covering of cemented sand, ex- hibiting two long posterior extensions which correspond in position with the siphons of the en- closed animal. These FIG. 5. Nest of Diplodonta orbella in empty extensions how- shell of Callithaca staminea Conrad. X 1. Courtesy Scripps Institution. ever, are not hol- low either, or at least are not originally hollow but most certainly are incrustations of stalks of plant material also! Thus the explanation of these extensions as siphon coverings, originated by Keep and carried along by Johnson and Snook, cannot be maintained and has to be given up in favor of their tentative explanation as anchoring ropes, as a protection against the action of the waves. My conclusions had come thus far, when it occurred to me that some information about the length and the general structure of the Diplodonta siphons might be important. It certainly was important, for the information I found, in Ball's words (1901, p. 795), is as follows: "There are two entire siphonal orifices, without siphons." Where there are no siphons, no siphonal coverings are needed; thus the explanation of the nest exten- sions as siphonal tubes is en- tirely baseless. Nothing is known as yet of the way in which Diplodonta orbella constructs its two kinds of coverings, though it ought not be too difficult to watch its construction in an aquarium. It is hoped that FIG. 6. Nest of Diplodonta orbella, from La Jolla, California. San Diego Mus. No. 1083. X 1. Courtesy San Diego Museum. 12 FIELD MUSEUM OF NATURAL HISTORY— ZOOLOGY, VOL. 29 my paper may stimulate some West Coast malacologist to study this interesting problem. I mentioned above that the myid bivalve Cooperella subdiaphana Carpenter also has the habit of constructing a protective covering. I have not found one myself, but I saw specimens both in the Los Angeles Museum and in the Stanford University Paleontological Collection; the latter is shown in figure 7. To the best of my knowledge, Keen and Frizzell (1939, p. 23) are the first to mention the Cooperella covering, describing it as a "nest of agglutinated FIG. 7. Nest of Cooperella subdiaphana Carpenter from Alamitos Bay, San Pedro, California. X 2. a, from side; b, from beneath. Courtesy Stanford University. sand"; but no picture of the object has ever been published. The dried covering is rather solid; it is closed all around, leaving only two slits on the posterior extremity open for the communication of the inmate with the outer world. ON SOME MEMBERS OF THE MYTILUS CALIFORNIANUS ASSOCIATION The California mussel certainly is one of the commonest, if not the commonest bivalve of the West Coast. Thanks to a compara- tively heavy shell and to strong byssus threads, the species is enabled to maintain itself even in habitats which, because of the heavy surf which beats them, would be uninhabitable for other mollusks. Wharf-piles and cliffs which otherwise would be almost destitute of an epifauna, may have a pad of mussels packed side by side and mostly covering the substratum. Other organisms which are not so perfectly protected against the surf action invariably settle on and between the California mussels and since the composition of this accompanying fauna is locally rather constant, we are entitled to speak of a well-defined "Mytilus californianus association," or, as 1943 MALACOLOGICAL NOTES— HAAS 13 it has also been termed, of a "Pisaster-Mytilus-Mitella association." (Ricketts and Calvin, 1939, p. 119.) I referred above to the species of the Mytilus californianus association as "locally constant"; this means that within the wide range of Mytilus californianus, which is only slightly affected by varying water temperature, its associated forms vary according to the great difference of the water temperature south and north of Point Conception. Some of these forms accom- pany the Mytilus in almost its whole range and some have their northern limit at Point Conception; on the other hand, northern species generally do not occur south of this point. This association is interesting for its complexity, but only one of the many problems involved is to be considered here, namely, the problem of settling. The union of so many animal species into the association with Mytilus californianus does not necessarily mean that its members cannot exist in other associations, without settling on or among Mytilus, ignoring at present the existence of relations between the California mussel and its associates so intimate as to suggest a tendency toward symbiosis or commensalism. To all the Mytilus dwellers, as we might call this epifauna, the mussel is nothing more than a rock, a substratum offering a place to settle on or offering crevices to hide in. This being so, we cannot expect to find in this association species other than those occurring on rocks either on the surf-beaten face or in sheltered recesses and crevices, according to their respective habits of life. The only sensible advantage derived by the Mytilus californianus epifauna from its living substratum is the increased amount of settling places in an appropriate environment. This has been discussed before, but it needs more detailed explanation. On sandy beaches, the larvae of sedentary animals, such as barnacles or pleurothetic bivalves, often cannot find a suitable place to settle at the end of their planktonic stage. Wharf-piles and occasional pieces of rock fallen from the distant edge of the cliffs will soon be covered by such forms, leaving no more space for later comers; but if Mytilus californianus has settled in such biotopes, their clusters will increase the available rock-like surface and permit additional larvae to metamorphose, which otherwise would have had to perish. The more thickly the forms that can stand the heavy surf cover the Mytilus substratum, the more recesses and quiet nooks between them come into existence, making a niche even for animals of the quiet water behind rocks. Thus most of the inhabit- ants of the tidal pools or of the protected coast may be found in the 14 FIELD MUSEUM OF NATURAL HISTORY— ZOOLOGY, VOL. 29 Mytilus californianus association, the small species as adult speci- mens, the larger ones, like crabs, as juveniles. Even in the case of mussels exposed to the full force of the incoming tide, the life con- ditions of the epifauna and the equally prospering epiflora of green and red algae may become so favorable that delicate forms charac- teristic of very quiet water, such as planarians or annelids, may be present, as we shall see from the list below. By way of a summary it may be stated that the California mussel association transfers the conditions of life of the tide-pools and the quiet recesses of the coast to those parts of open, shelterless beaches where Mytilus can find a primary station. The following list does not presume to give a complete enumera- tion of the epifauna of the California mussel; it shows the variety of animal life found on one single specimen (Field Museum No. 16595) of Mytilus (Aulacomya) californianus Conrad, of a length of 73 mm., collected April, 1941, on the seaward face of a pile of the pier at La Jolla, California: Planaria Prosthiostomum sp. Actinia Cribrina xanthogrammatica Brandt Annelida Nereis vexillosa Grube Eupomatus sp. Bryozoa Retepora padfica Robertson Cirripedia Mitella polymera Sowerby (young) Chthamalus fissus Darwin Isopoda Cirolana harfordi Lockington Anomura Pagurus hirsutiusculus Dana Petrolisthes cinctipes Randall (young) Petrolisthes eriomerus Stimpson (young) Brachyura Hemigrapsus oregonensis Dana (young) Mollusca Ostrea (Ostreola) lurida Carpenter Mytilus (Aulacomya) californianus Conrad (young) Brachidontes (Hormomya) adamsianus Dunker (young) Lasaea subviridis Dall Littorina (Melaraphe) planaxis Philippi Acmaea (Collisella) scabra Reeve Acmaea (Collisella) asmi Middendorff Nuitallina scabra Reeve The number of species listed is not high compared with that which Carpenter (1857, p. 154) found on one single upper valve of Spondylus calcifer from Mazatlan, which included 102 species of mollusks alone! But S. calcifer is a much larger bivalve than our California mussel and it has a very thick shell into which part of the members of its epifauna drill their holes. Nor can the above list compete with that published by Perry (1936) enumerating the animals found on one Atrina rigida shell from the Gulf waters of 1943 MALACOLOGICAL NOTES— HAAS 15 Florida, which contained no less than 25 species belonging to eight different phyla of animals and represented by more than 100 individ- uals; but though the Atrina shell is even thinner than that of Mytilus calif or nianus, the higher number of epizoan forms on the former is due to its greater surface, amounting to nearly 150 sq. cm. The species enumerated in our list are by no means the only Mytilus dwellers, for on or among other specimens of the Cali- fornia mussel from La Jolla, I collected the following species; and I am fully aware that a great many more species, almost the whole of the still-water fauna, have escaped my attention and are not listed here. Hydroidea Scala (Globiscala) orcuttiana Dall Orthopyxis compressa Clark Lasaea cistula Keen Septifer brfurcatus Conrad Molluscs Haminea (Haminea) virescens Sower- Annelida by Eunice biannulata Moore Mitronwrpha filosa Carpenter Halosydna calif ornica Johnson Crepidula (Janacus) nummana Gould Cythara (Mangelia) cesta Dall _ Columbella (Alia) gausapata Gould Ecnmodermata Acmaea (Collisella) persona Esch- Pisaster ochraceus Brandt scholtz Amphipholis pugetana Lyman As has been pointed out, the settlement of the Mytilus substratum, i.e., the formation of the Mytilus californianus association, takes place in two steps. The first step is represented by the settling of sedentary animals — barnacles, oysters, bryozoans, etc. — on the pre- viously uninhabited mussel shells. The second step is characterized by the arrival of free-living, non-sessile animals such as annelids, isopods, crabs, etc., in the corners and nooks between the first series of arrivals. The creatures belonging to these two different groups of Mytilus dwellers have very different habits of life and their be- havior toward each other is not that of friendly neighbors. For while the members of the first, the sedentary group, are all of them plankton feeders, those of the second, the roving group, are pre- daceous animals, preying on each other and on their sessile neighbors. The starfish, especially, are the deadly enemies of the California mussel. The plankton feeders, though they do not devour each other, are nevertheless competitors for food. Where, in a given association, there are two or more layers of such sessile creatures, the lower, the original and older, may be starved by the upper ones, which gather all the nutritive particles contained in the sea water before it reaches the lower stratum. In addition to such starvation, the 16 FIELD MUSEUM OF NATURAL HISTORY— ZOOLOGY, VOL. 29 forms of the lower layers may be choked to death by the weight of the later settlers. Thus the Mytilus californianus association is by no means a community of beings respecting each other, but a community like every other, with competition for food, and with certain death for the weaker. In other words, it is a typical biocenosis, in which only the strongest or the best-protected individuals survive. In southern California, the most obvious mollusk accompanying this association is another mytilid, characterized by a radiating sculpture on its shell. Its name is Mytilus (Hormomya) adamsianus Dunker, but it is often quoted in the literature as Mytilus multi- formis Dunker or Mytilus stearnsii Pilsbry and Raymond; it is not a true Mytilus, but has to be placed in the subgenus Hormomya Moerch, whose type species is the Atlantic Mytilus exustus Linnaeus. Intermixed with the Mytilus adamsianus in the same association, but generally in much inferior numbers, lives another sculptured mytilid, very similar to adamsianus in size and shape, but actually very different: Septifer bifurcatus Conrad. At the present time, only Mytilus adamsianus interests us, since, at La Jolla, it is the host shell of two probably commensal bivalves of the genus Lasaea, L. cistula Keen and L. subviridis Ball. Both species are rather common at La Jolla, and I found them there exclusively on the shell or the byssus of Mytilus (Hormomya} adamsi- anus; not a single specimen lived on Septifer or, with one restriction to be pointed out immediately, on the much more abundant Mytilus (Aulacomya) californianus! This statement fully agrees with an earlier observation made by Charles R. Orcutt who, according to a notice on a label in the San Diego Museum, collected Lasaea on Mytilus adamsianus. Several lasaeas, however, were detected in dead Donax shells or in cups of Balanus, or even on Mytilus cali- fornianus, but on these objects one or several specimens of Mytilus adamsianus had fastened their byssus, so that even in these seemingly aberrant habitats the close relation with this mytilid is maintained. An association analogous to that of the California mussel is developed in Peruvian waters, where Mytilus californianus is re- placed by its close relative, M . magellanicus Chemnitz, and Mytilus adamsianus by the almost identical Mytilus granulatus Hanley. In a thick bunch of a Mytilus magellanicus association scraped off from rocks at Chincha Norte Island, Peru, by Mr. William Vogt, Mytilus granulatus was represented by a fair number of specimens and on them, and exclusively on them, some lasaeas were found which I 1943 MALACOLOGICAL NOTES— HAAS 17 have provisionally classified as Lasaea miliaris Philippi, though they are practically inseparable from the North American Lasaea cistula Keen; the specific name, however, is of no importance relative to the fact that in this Peruvian locality a species of Lasaea restricts its habitat to a mytilid which constitutes only a minority among the leading species of the association. In spite of this supporting case from Peru, the observation made in southern California, at La Jolla, that Lasaea does not live in close community with the commonest mytilid, but only with an accompanying species, cannot be generalized. North of Point Con- ception, Mytilus adamsianus does not occur, its place in the Mytilus californianus association being vacant. But both the species of Lasaea are found north of Point Conception, and at Pacific Grove, the only locality north of this point where I collected, I found them on the shell and on the byssus of the dominant Mytilus californianus itself! The only possible explanation of this strange behavior is that while the lasaeas prefer adamsianus to all other host shells, Mytilus californianus is a second choice, to which they attach them- selves when no adamsianus is available; but the details of their supposedly commensalistic relation to these mytilids are still entirely unknown. Yet the fact that Lasaea in European waters is known as a commensal of sea-urchins and snails makes it more than probable that northwestern American lasaeas may also enter into commensa- listic relations. For the sake of completeness, it must be mentioned that at Pacific Grove I washed out both species of Lasaea from fastholds of kelp, where they cannot have led a commensalistic life and where they must have retired for protection only. My failure to detect free-living lasaeas in similar habitats at La Jolla by no means proves that they cannot occur there. A RECORD OF ALABA INTERRUPTELINEATA Alaba interruptelineata is the most recently described species of a genus indiscriminately attributed either to the family Cerithiidae or to the Litiopidae (Pilsbry and Lowe, 1932, p. 81) and has been known only from San Juan del Sur, Nicaragua, the type locality. A specimen of this species (Field Museum No. 16562) was found by Loren P. Woods, Assistant Curator of Fishes, in the mouth of a sparid fish collected at Guaymas, Sonora, Mexico, by Messrs. Kenneth Curtis and John Clay. This Guaymas specimen fits the original description of the species perfectly, except for being 6 mm. 18 FIELD MUSEUM OF NATURAL HISTORY— ZOOLOGY, VOL. 29 long instead of 7; the number of whorls is identical with that of the figured type. RECORDS OF MOLLUSKS FROM FLORIDA Mr. Alfred C. Weed, formerly Curator of Fishes, brought home from his Florida trip in 1939, among other mollusk material, two species of shells which have not often been recorded from that state. Notarchus (Aclesia) pleii Rang This Antillean opisthobranch snail is apparently recorded only from the following Florida localities: Little Gasparilla Bay, Charlotte County, collected by Wilcox and Heilprin, quoted from Pilsbry's Manual of Conchology, (1), 16, p. 148, 1896. Marco, Collier County, (C. W. Johnson), Proc. Bost. Soc. Nat. Hist, 40, p. 150, 1934. I am indebted to Mr. T. Van Hyning, Director of the Florida State Museum, Gainesville, Florida, for the following records: Cedar Key, Levy County; St. Petersburg, Pinellas County; Lake Worth, Palm Beach County; South Lake Worth Inlet, Palm Beach County. Mr. Weed collected this species in various parts of Lemon Bay near Englewood, Charlotte County, Florida, in the vicinity of the Bass Laboratory (Field Museum No. 17020). Auriculastra pellucens Menke This species is apparently restricted to the Caribbean region. It has been recorded from Demerara, British Guiana, the Lesser Antilles, and Florida. In Florida it has been found frequently on the Gulf shore of the peninsula as far as Cedar Keys, while, to the best of my knowledge, it has been mentioned only once from the Florida east coast, where S. N. Rhoades collected it near Miami (Nautilus, 13, p. 47, 1899). Field Museum recently received two dead shells of A. pellucens (Field Museum No. 16339), collected in 1938 at North Miami Beach by Mr. Weed, who describes the locality where he picked up the specimens as a former salt marsh close to the beach, now re- claimed by a low levee. Two species of land gastropods, Polygyra (Daedalocheila) uvulifera bicornuta Pilsbry, and Polygyra (Polygyra) cereolus septemvolva Say, were associated with it. Mr. T. Van Hyning has kindly forwarded his list of localities prepared for his own forthcoming catalogue of Florida Mollusca for 1943 MALACOLOGICAL NOTES— HAAS 19 my examination. His list confirms the scarcity of A. pellucens on the Atlantic coast. ADDITIONS TO THE MOLLUSK FAUNA OF BERMUDA Since the appearance of my "Additions to the Mollusk Fauna of Bermuda" (1941, p. 171), some additional material collected by T. H. Bean in the course of the Field Museum Expedition to Bermuda in 1905 has come to hand, the classification of which has brought to light various species of marine mollusks hitherto not recorded, or only doubtfully recorded, from the Bermuda Islands. Musculus (Gregariella) coralliophagus Gmelin A single specimen of this species, referred to as divaricata Philippi in most faunal lists, from the Challenger Bank, 28 fms. Field Mu- seum No. 16430. Pecten (Nodipecten) antillarum Recluz A single valve from the Challenger Bank, 28 fms., corresponding in all details with the description of this species. Field Museum No. 16445. Area (Barbatia) reticulata Gmelin Three species from the Flats. Field Museum No. 16442. A single valve from Mullet Bay, St. George's Island. Field Museum No. 16441. Chama (Chama) congregata Conrad One specimen from Challenger Bank, 28 fms. Field Museum No. 16428. Peile (1926, p. 96) mentions Chama lingua felis Reeve with a hint that it may be a young macerophylla Gmelin; in a personal note he writes me that probably it is C. congregata that is meant. Gastrochaena (Gastrochaena) hians Chemnitz A dead shell from the Challenger Bank, 28 fms. Field Museum No. 16436. One specimen collected alive at Pegg's Island, St. George's Harbor, still in the piece of rock. Field Museum No. 16437. These records support the doubtful quotation of this species by Peile, under the name of G. cuneiformis, which rested solely on Ball's authority. 20 FIELD MUSEUM OF NATURAL HISTORY— ZOOLOGY, VOL. 29 Erosaria (Ocellaria) spurca Linnaeus Two specimens from the Challenger Bank, 28 fms. Field Mu- seum No. 16482. WHAT IS EXILIBERUS JACKSONI IREDALE? Under the above name Iredale (1942) recently has described a land snail from the Libyan Desert that he believed to stand quite isolated in the Egyptian fauna. From his description (unfortunately not accompanied by a figure) it is evident that the shell in question belongs to that keeled and wrinkled phase of the helicid genus Eremina Pfeiffer of which E. zitteli Boettger is the classical repre- sentative (see Boettger, 1899; Kobelt, 1900, 1902). This phase is so strikingly different from typical Eremina with its keelless, smooth- ish shell that its subgeneric separation, under a special name, might be justified, in which case the name Exiliberus would be acceptable. But the sharp-keeled and the keelless phases are linked together by insensible intergradations, as demonstrated by Kaltenbach (1934) who thus proved Eremina zitteli to be only an extremely modified form of E. hasselquisti Ehrenberg. This chain of forms has a com- plete analogon in the Spanish Iberus alonensis FeYussac, whose globular, smooth and rounded shell locally passes gently and almost insensibly into that of the lens-shaped, sharply keeled and wrinkled Iberus gualtierianus Linnaeus (see Kobelt, 1910). In the latter series, the anatomy supports the conchological judgment, whereas in Eremina the keeled phase has not yet been dissected; the shell characters, however, are sufficient to keep the zitteli phase, to which Iredale's Exiliberus jacksoni belongs, within the genus Eremina proper. Exiliberus is thus a synonym of Eremina. As to the species jacksoni, it cannot properly be allocated with- out more material and a more exact type locality than "Libyan Desert." It may be typical zitteli or one of the transitory forms passing into zitteli; it may represent a valid form worthy of nomen- clatorial distinction. A HIRSUTE PHASE OF POLYGYRA (DAEDALOCHEILA) IMPLICATA MARTENS Among other valuable shells collected by Mr. David W. Berg- strom in Mexico during the summer of 1941, some specimens of Polygyra (Daedalocheila) implicata Martens are especially note- worthy. They were collected near Tamazunchale, five miles south of that city, and ten miles south of the city of San Luis Potosi, in the state of San Luis Potosi; they are recorded in Field Museum Collection under the numbers 17802-17804. Though otherwise quite 1943 MALACOLOGICAL NOTES— HAAS 21 FIG. 8. Polygyra (Daedalo- cheila) implicate Martens, hirsute phase. Field Mus. No. 17803. X 5. typical, these specimens differ from existing descriptions and figures by the short but distinct hairs on their shell surface; figure 8, about five times actual size, demonstrates this feature.1 Such hairiness is a feature not unknown in the family Polygyridae and is even normal in some daedalocheilas; the whole section Lobos- culum Pilsbry for instance is hirsute. J. K. Strecker (1908, p. 66) mentioned the discovery of a hairy "variety" of P. (Daedalocheila) mooreana W. G. Binney in a stone pit near Waco, Texas. Pilsbry (1940, p. 624) suggests a possible confusion with the normally hir- sute P. (Lobosculum) leporina Gould. Perhaps my own report of a hairy phase of P. (Daedalocheila implicata gives additional support to Strecker 's statement. The question as to whether the hairy phases of daedalocheilas occur only in isolated populations or side by side with smooth specimens, cannot, at present, be solved ; thus the secondary question as to whether these hairy forms are entitled to nomenclatorial dis- tinction as subspecies, though relevant, cannot yet be settled. In a somewhat analogous European case, that of the helicid snail Helicigona (Chilostoma) desmoulinsi Farines with its hirsute phase acrotricha Fischer, the ranges of the two phases do not overlap or overlap only slightly. Thus, typical desmoulinsi becomes the representative in the Pyrenean region in general, with the exception of the massive of the central Pyrenees, where H. (Chilostoma) desmoulinsi acrotricha occurs exclusively. Further research may reveal similar relations in other families of land snails, so, for instance, in some other helicigonines of Europe, in the Asiatic pleurodontid genus Chloritis, or in the likewise Asiatic ariophantid genus Hemitrichia. From an evolutionary point of view, the possession of hairs seems to be a primitive character in snails, and where there are hirsute and naked phases in the same species or group of species, the unhaired phase is, probably, the younger and the more advanced, as in some other helicigonines of Europe, in the pleurodontid Asiatic genus Chloritis, or in the likewise Asiatic ariophantid genus Hemitrichia. 1 1 am indebted to Mr. John Bayalis for the photograph of this specimen. REFERENCES BAILY, J. L., JR. [EDITOR] 1935. West Coast Shells. A description in familiar terms of the principal marine, fresh-water, and land mollusks of the United States, British Columbia, and Alaska, found west of the Sierra. By Josiah Keep, revised by Joshua L. Baily, Jr. Stanford University Press. 350 pp., 334 figs. BOETTGER, OSKAR 1899. Eine neue Eremia aus der Oase Siuah. Nachr. Bl. Deutsch. Mai. Ges., 31, pp. 158-160. CARPENTER, P. P. 1857. Catalogue of the Collection of Mazatlan Shells in the British Museum, collected by Frederick Reigen. London. 552 pp. DALL, W. H. 1901. Synopsis of the Lucinacea and of the American Species. Proc. U. S. Nat. Mus., 23, pp. 779-833, pis. 39-42. DALL, W. H. and BARTSCH, P. 1909. Monograph of the West American Pyramidellid Mollusks. Bull. U. S. Nat. Mus., 68, pp. 1-258, pis. 1-30. HAAS, FRITZ 1941. Malacological Notes— II. Field Mus. Nat. Hist., Zool. Ser., 24, pp. 167-174, pis. 1-2. IREDALE, TOM 1942. Description of a Libyan Desert Land Shell. Rec. Aus. Mus., 21, p. 126. JOHNSON, M. E. and SNOOK, H. J. 1927. Seashore Animals of the Pacific Coast. New York. 659 pp., 700 figs., 11 pis. KALTENBACH, H. 1934. Die individuelle, okologische und geographische Variabilitat der Wiisten- schnecken Eremina desertorum, hasselquisti und zitteli. Arch. Naturg., (2), 3, pp. 383-404, 7 figs. KEEN, A. M. and FRIZZELL, D. L. 1939. Illustrated Key to West North-American Pelecypod Genera. Stanford University Press. 28 pp., figs. KEEP, JOSIAH 1893. West Coast Shells. A familiar description of the marine, fresh water, and land mollusks of the United States, found west of the Rocky Mountains. San Francisco. 230 pp., 182 figs., 1 pi. 1904. West Coast Shells. A description in familiar terms of the principal marine, fresh water, and land mollusks of the United States, found west of the Rocky Mountains, including those of British Columbia and Alaska. San Francisco. 360 pp., 303 figs., 1 pi. 1911. West Coast Shells (Revised Edition). A description of the principal marine mollusks living on the west coast of the United States, and of the land shells of the adjacent region. San Francisco. 436 pp., 300 figs., 5 pis. 1935. See BAILY, J. L., JR. KOBELT, W. 1900. In Martini-Chemnitz, 111. Conch. Cab., (2), 1, Abt. 12, vol. 5, Die Familie der Heliceen, p. 944, pi. 245, figs. 1-3. 22 1943 MALACOLOGICAL NOTES— HAAS 23 1902. In Rossmaessler, Iconographie der Land- und Siisswasser Mollus- ken . . . , (2), 9, p. 29, pi. 252, fig. 1624. 1910. In Rossmaessler, Iconographie der Land- und Siisswasser Mollus- ken . . . , (2), 15, pp. 10-12, pis. 396-398. KtJHNELT, W. 1930. Bohrmuschelstudien. I. Palaeobiologica, 3, pp. 53-91, 7 figs., pis. 4-11. ORCUTT, C. R. 1915. Molluscan World. San Diego. 1, 208 pp. PEILE, A. J. 1926. The Mollusca of Bermuda. Proc. Mai. Soc. Lond., 17, pp. 71-98, 4 figs. PERRY, L. M. 1936. A Marine Tenement. Science, (2), 84, pp. 156-157. PlLSBRY, H. A. 1940. Land Mollusca of North America (North of Mexico). Acad. Nat. Sci. Phil., Monogr. No. 3, 1, pt. 2, pp. 575-994, 203 figs. — and LOWE, H. N. 1932. West Coast and Central American Mollusks Collected by H. N. Lowe 1929-1931. Proc. Acad. Nat. Sci. Phila., 84, pp. 33-144, 7 figs., pis. 1-17. RICKETTS, E. F. and CALVIN, J. 1939. Between Pacific Tides. An account of the habits and habitats of some five hundred of the common, conspicuous sea-shore invertebrates of the Pacific Coast between Sitka, Alaska, and northern Mexico. Stanford Uni- versity Press. 320 pp., 112 figs., 64 pis. SHEPARD, I. M. 1895. With a Dredge. Nautilus, 9, pp. 71-72. STRECKER, JOHN K., JR. 1908. The Mollusca of McLennan County, Texas. Nautilus, 22, pp. 63-67.