ECOLOGICAL AND SYSTEMATIC NOTES ON FROM ST. CROIX, U. S. VIRGIN ISLANDS!

DONALD R. MOORE University of Miami, Rosenstiel School of Marine and Atmospheric Science

ABSTRACT A survey of the shallow marine fauna at St. Croix, U.S. Virgin Islands, was made in the summers of 1969 and 1970. Sediment samples were collected by diving, and were picked from them. The Cae- cidae were studied from shallow-bay sediments and a quantitative study was made at three slightly deeper stations in and around the coral reefs. Seven of Caecidae, 268 specimens, were found in 176 cc of sedi- ment from the three stations in deeper water. An eighth species was rare in the area of shallower water. The eight species, condylum Moore, C. subvolutum Folin, C. lineicinctum Folin, C. regulare Carpenter, C. textile Folin, C. imbricatum Carpenter, C. () nitidum Stimpson, and C. (M.) cornucopiae (Carpenter), are all poorly known. The first three species do not live in back-reef or lagoonal areas, and so were supposed to be extremely rare. However, these three species comprised 55 per cent of the Caecidae from the three stations in deeper water. They live in an environment that has been little sampled, so have been seldom collected. Distribution for all of the species is tropical, although C. nitidum and C. imbricatum are found in the northern Gulf of Mexico as well.

INTRODUCTION Two brief surveys of the shallow marine environment of northeastern $1. Croix were undertaken by Dr. H. Gray Multer, Dr. Wayne D. Bock, and myself in 1969 and 1970. Dr. Donald Marszalek and Cynthia Moore also participated in the 1970 survey. Observations and colIections were made on the reef, on grassy bottom, on open sandy bottom and along the rocky shore. In addition to some macroinvertebrates, sediment samples were collected at selected sites in depths ranging from one to about 20 m. The area surveyed (Figs. 1 and 2) forms a triangle, with the east end of Buck Island at the apex, and Tague Bay and Cottongarden Point re- spectively occupying the west and east ends of the base line. Sediment samples were obtained by diving during 1969; in 1970, the samples were collected by diving and by the use of a small clamshell bottom sampler in two transects from Buck Island to S1. Croix. A series of samples taken in shallow water inside the reef were picked and sorted during 1969. In this area, some 27 species of micromollusks ranging in size from 0.8 to around 5.0 mm were identified, and several additional species are still

1Contribution No. 1562 from the University of Miami, Rosenstiel School of Marine and Atmo- spheric Science, and Contribution No. 4 from the West Indies Laboratory, Fairleigh Dickinson University. 882 Bulletin of Marine Science [22(4)

FIGURE 1. Map of St. Croix, U. S. Virgin Islands, showing fringing reefs en- closing the shallow bays. The reefs are concentrated around the eastern two- thirds of the island. unrecognized. For 1970, it was decided to study the fauna in somewhat deeper water around, and in front of, the reef. Two samples from 12 m and one from about 14 m were picked and the micromol1usks studied. Allor most of each sample was picked in order to obtain as many species as possible. This sediment was almost entirely calcareous in origin, and was derived from algae and the shelled inverte- brates living in the area. The important elements were mollusks, Foram- inifera, the alga Halimeda, coral fragments, crustacean exoskeletons, and, more rarely, sponge spicules, brachiopods, and echinoderm fragments. A few of these were living in situ, but most were evidently living on hard bottom close by. After the death of these animals, water move- ment carries the shells a few meters to the low places, where they accumu- late as calcareous sediment. At first, it was planned to contrast the micro molluscan faunas living in the fore reef and back reef areas. Too many systematic problems have, however, caused a revision of these plans. Groups of species will be reported on as their is worked out, and will be reported in a series of short papers. This is the first of the series. One 12-m sample came from the open bottom in front of the reef stretching across Tague Bay. The second 12-m sample came from the eastern end of Buck Island about 2.5 km north of the first locality. The third locality was about 200 m southeast of the second, and was taken from a depth of about 14 m. The two Buck Island localities were close to towering mounds of coral (Montastrea, Diploria, and Acropora), while the Tague Bay locality was at the foot of a long gradual reef slope. All of the species of Caecidae here considered are very poorly known, so they will be discussed in some detail. The first species was only described in 1972] Moore: Caecidae from St. Croix 883

BUCK is.

ST. eR.OI X

FIGURE 2. Map of the eastern end of St. Croix showing Tague Bay and Buck Island. The three deeper water stations are marked (see text for localities).

1969 from two specimens, hence its discovery in some abundance at St. Croix is of interest.

SYSTEMATIC AND ECOLOGICAL NOTES Caecum candylum Moore, 1969 Fig. 12 Caecum condylum Moore, 1969, Nautilus, 83(1): 26-28, one fig. Type-Locality.-Payardi Island, near Colon, on the Atlantic side of Panama. Material.-Tague Bay: 5 specimens; Buck Island, 12 m: 2 specimens; Buck Island, 14 m: 27 specimens. Description.- The teleoconch is cylindrical and slightly curved for most of its length. The anterior part is more strongly curved and there is a broad, rounded swelling near the aperture. The septum is slightly de- pressed and the low, somewhat pointed mucro is angled to the right. Sculp- 884 Bulletin of Marine Science [22(4)

FIGURES3-5.-3, Caecum lineicinctum Folin, length 2.44 mm, seen from the right side. This specimen has been bored by a small carnivorous gastropod.- 4, C. subvolutum Folin, length 2.18 mm.-5, C. lineicinctw/1, another view, to show sculpture at the anterior end of the shell. ture consists of approximately 100 low, close-set annular ridges which are all about the same width. The shells are almost transparent when fresh, and bear two or three diffuse brown bands. The operculum was not observed. Remarks.-None of the specimens of C. condylum was mature and in good condition. The specimens were either short second-stage, immature third-stage, or broken mature specimens. Since all of the adults were broken, this suggests that some enemy, possibly a crab, is a heavy predator on C. condylum. All of the other species of Caecum were represented by adults in good condition. As I had predicted, even second-stage specimens of C. condylum were easy to recognize, since no other western Atlantic species has a shell with so many close-set ridges. 1972] Moore: Caecidae from St. Croix 885 Fresh specimens of C. condylum are shining and almost transparent; the brown bands are quite striking on these individuals. None of the specimens was alive when collected, for the species probably lives on the hard substrate adjacent to the sandy patch from which the sediment was collected. Samples of shallow-water sediment inshore from the reef did not contain specimens of C. condylum. Apparently, this is a true coral- reef species which shuns the shallow reef flat area, but which is abundant at depths of more than 10m. The maximum depth probably coincides with the greatest depth of coral reef development, or around 40 m in the Caribbean. The distribution of C. condylum will probably take in the entire tropical West Indian area when proper collecting is done. The pres- ent record establishes the species 15° farther east than in the original paper. Caecum subvolutum Folin, 1874 Fig. 4 Caecum subvolutum Folin, 1874, Fonds de la Mer, 2: 277, pI. 10, figs. 6-7. Type-Locality.-In 100 fm (183 m), west of Barbados, a few miles north of Bridgetown; Hassler Expedition. Material.-Tague Bay: 11 specimens; Buck Island, 12 m: 34 specimens; Buck Island, 14 m: 47 specimens. Description.-The shell is slender, smooth, and cylindrical for most of its length. A rather thick brown periostracum is present on fresh specimens. Curvature of the shell is moderate, but stronger at the anterior end. There is a low varix at the aperture, bearing several minute annular ridges. The septum is slightly recessed and bears a strong flattened mucro. A large adult measured 2.25 mm long and 0.4 mm in diameter at the middle of the shell. There is no color, although the shell turns white sometime after the death of the . Remarks.-At first glance, this species might be mistaken for C. condy- lum. C. subvolutum, however, has a much stronger mucro projecting at a higher angle, is smooth or nearly smooth except on the varix, and docs not have bands of color. The holotype is in the Folin Collection at the Laboratoire de Malaco- logie in Paris. The mucro in Folin's drawing is exaggerated. The type itself was damaged and repaired near the aperture, but several small annular ridges are visible on the varix. The specimen was in all probability carried down from shallow water and did not live where it was collected. It was not a fresh specimen and showed signs of wear. The species apparently ranges from Barbados to Florida. Two worn specimens that are apparently this species were collected off Miami in 162 fm by the University of Miami ship GERDA. 886 Bulletin of Marine Science [22(4) Caecum lineicinctum Falin, 1879 Figs. 3, 5 Caecum lineicinctum Falin, 1879, Proc. zool. Soc. Lond., 1879: 808. Type-Locality.-CHALLENGER station 24, 18°38'30"N, 65°5'30"W, 390 fm (715 m), north of Culebra. Material.-Tague Bay: 9; Buck Island, 12 m: 5; Buck Island, 14 m: 13. Description.-The shell is stout, strong, and smooth except for several weak annular ridges near the anterior end. These are followed by a moderate-sized varix bearing several more annular ridges. The septum is deeply recessed, and the fingerlike mucro projects almost straight out. It is not sharply pointed as in C. floridanum, but curves out- ward slightly and ends in a blunt point. Adult specimens are a translucent white in color. A large specimen measures 2.88 mm long, by 0.64 mm in the middle. Remarks.-C. lineicinctum was described from a single, not quite mature, specimen which is in the British Museum (Natural History). The speci- men was taken by the CHALLENGERat Station 24, depth 390 fm (715 m), off the island of Culebra, just east of Puerto Rico. This station was made close to shallow water, and evidently shallow-water sediments had washed down from the bank. At least one other shallow-water species was described from this haul. C. lineicinctum is similar to C. carolinianum Dall, but is smaller and partly sculptured, whereas C. carolinianum is large, thick shelled, and usually smooth all over. The recessed septum and blunt-tipped mucro, however, are very similar in the two species. C. lineicinctum might be confused with C. subvolutum, but the latter species is much more slender, has a weak varix which does not begin abruptly, and has a low flattened mucro on a slightly recessed septum. C. lineicinctum, on the other hand, has a deeply recessed septum with a fingerlike mucro. This is apparently the first report of C. lineicinctum since the original description almost a century ago. In addition to the type-material and the present material, whose collection localities are separated by only a few miles, several other specimens have been found in other areas. Germaine Warmke sent me three specimens dredged in 91 m off Punta Jiguero, western Puerto Rico, and Gordon Nowell-Usticke sent in six specimens dredged at Antigua. The known distribution of the species is thus con- fined to the northeastern corner of the Caribbean, but further investigation may show that its range is greater. These first three species, Caecum condylum, C. subvolutum, and C. 1972] Moore: Caecidae trom St. Croix 887 lineicinctum, have all been extremely rare and poorly known. It can now be seen that they live on the front slopes of reefs, and that their shells accumulate in sandy low spots after death (none of the above-mentioned specimens was alive at time of collection). This niche is poorly sampled in tropical regions. Little dredging is done in this area, since much of the bottom is rocky and the sand is found only in pockets. We now know that C. condylwn lives over a vast area in the West Indian region. C. sub- volutum has been found off the Florida coast, far from the type-locality off Barbados. This leaves C. lineicinctum as the most restricted of the three, but this may be just an artifact of collecting. Both C. lineicinctum and C. subvolutum were described from single specimens in poor condition. Both specimens were from rather deep water (715 and 183 m), hence it was something of a surprise to find both spe- cies at a depth of 12 m. Apparently all of the Caecidae live in compara- tively shallow water in depths seldom exceeding 100 m. All records of great depths have been made at the bases of steep slopes close to land or to shallow banks. The greatest depth yet reported, TALISMANdredge sta- tion No. 144, 2995 m, was based on a single specimen described as C. devium by Folin (1887). This station was just north of Sao Miguel in the Azores. The CHALLENGERalso took a single specimen in poor condi- tion (fortunately, not named) southeast of Sao Miguel in 1830 m (Sta. 78, July 10, 1873). Both specimens were undoubtedly washed down the steep slopes from shallow water. A few Caecidae may live out to the edge of the Continental Shelf under proper conditions, but I seriously doubt that any will be found living in deeper water. The other five species in this report are common in shallow water and may be found from the reef zone to the shore.

Caecum regulare Carpenter, 1858 Fig. 7 Carpenter, 1858, Proc. zool. Soc. Lond., 1858: 428-429. Type-Locality.-West Indies is the first locality given by Carpenter, other localities are Singapore and Australia. Material.-Tague Bay: 12; Buck Island, 12 m: 14; Buck Island, 14 m: 18. Uncounted specimens were found in all of the Cottongarden Point samples, and in a series of samples across Tague Bay from the reef to the shore. Description.- The shell is moderately thick and strong. Sculpture consists of 25 to 30 flat-topped annular ridges. The ridges are about as wide as the interspaces on the sides of the shell. They can best be counted on the convex dorsal part of the shell. No trace of a varix is present. 888 Bulletin of Marine Science [22(4)

7

FIGURES 6-7.-6, Carpenter, length 2.36 mm, seen from the left side. The smooth area is the result of an attack by a predatory gastro- pod; for some reason the drilling was not completed.-7, C. regulare Carpenter, length 1.76 mm.

The septum is even with the posterior end of the teleoconch. The mucro is small and bluntly pointed. There is a distinct light brown periostracum on fresh specimens. A large specimen measures 2.14 mm long by 0.6 mm at the aperture. Remarks.- The identity of Caecum regulare has long been a problem. The vague type-locality, West Indies, is of little help since there appear to be several very similar species in the Caribbean area. Carpenter (1858), in his monograph of the Caecidae, stated that most of his West Indian material came from sponges. According to Moore (1923), the world's sponge supply came entirely from the Mediterranean before 1841. In that year a French sponge merchant was wrecked in the Bahamas and noticed the quality of the native sponges. A sample lot was shipped to 1972] Moore: Caecidae from St. Croix 889 Paris, and by 1850 the value of exported sponges was about $10,000 per year. Carpenter's sponges were thus presumably shipped from Nassau, the capital of the Bahamas. All of the West Indian species described by Carpenter in the Monograph have been found around New Providence Island, where Nassau is situated, so I hereby designate the shallow waters around New Providence as the type-locality for these species. The list of new species described by Carpenter which will take this as type-locality are as follows: Caecum plicatum C. dextroversum antillarum C. imbricatum C. (Meioceras) nitidum C. gurgulio C. (M.) cornucopiae C. regulare C. (M.) cornubovis Of this list, all except C. regulare and M. cornubovis are reported as found in shell sand from sponges. Carpenter described C. regulare as having 20 to 24 annular ridges. My counts on a series of 17 specimens from near Coakley Town, Andros Island, are consistently higher than this. The higher count is probably due to the inclusion of two or three smaller ridges around the aperture; I also made sure that the specimens were fully mature. In other respects, my speci- mens fit the description and the unpublished figure drawn by Carpenter. C. regulare is usually found with C. gurgulio in the Bahamas. C. gur- gulio is very similar in size and appearance, but has low, flat, close-set ridges which number around 36 in a mature specimen. The periostracum is not noticeable in C. gurgulio, but it is fairly thick and brown in fresh specimens of C. regulare. As yet, C. gurgulio has not been found at St. Croix, so C. regulare can be recognized with ease from sediment samples from St. Croix. The species problem makes it difficult to give the range of C. regulare. I have collected specimens that I consider to be this species from southeast Florida, from the north central Bahamas, and from the Virgin Islands. A closely related species from Florida and the Gulf of Mexico is probably C. pulchellum.

Caecum textile Folin, 1867 Figs. 8, 9 Caecum textile Folin, 1867, Fonds de la Mer, 1: 21-22, pI. 2, figs. 8, 9. Caecum leptoglyphos Folin, 1881, Fonds de la Mer, 4: 48, pI. 3, fig. 5. Type-Locality.-Guadeloupe. The type-locality of C. leptoglyphos is also Guadeloupe. Material.-West side of Cottongarden Point: 1; behind outer reef, Tague Bay: 1. 890 Bulletin of Marine Science [22(4 )

FIGURES8-9. Caecum textile Folin: 8, specimen from Ajax Reef in the Florida Keys; length 1.92 mm; 9, enlargement of a small area near the center of the same specimen.

Description.- The shell is moderately thick and strong. The sculpture consists of about 35 to 45 very low, rounded ridges. Interspaces, even on the convex side of the shell, are not as wide as the ridges. Over the annu- lar ridges are numerous fine longitudinal striae. The circular ridges are so low that most specimens appear almost smooth. There is no varix. The septum is even with the posterior end of the te1eoconch. Scen from the right side, the profile of the mucro varies from slightly to strongly convex. It terminates in a bluntly rounded point. A large specimen from Soldier Key, Florida, measures 2.1 mm long by 0.52 mm near the aperture. Remarks.-It seems strange that Falin would redescribe his species when all of his material came from Guadeloupe. However, there are no speci- mens of C. textile in the Folin collection in Paris, and the species is not listed in the catalog of Folin's material published in 1880. Kisch (1959) 1972] Moore: Caecidae from St. Croix 891 mentioned that there are four specimens of C. textile in the British Mu- seum, sent there by Folin in 1868. Kisch considered these specimens to be syntypes. Apparently, Folin forgot his prior description, or was misled by his figure of C. textile. Caecum textile appears to be a species confined to a warm, stenohaline environment. All specimens so far collected by me have been found in shallow water around coral reefs. The species may be confused with C. gurgulio in southern Florida and the Bahamas, but, as yet, no specimens of C. textile have been found in the Bahamas. The range of C. textile now extends from South Florida to Guadeloupe, and probably includes most Caribbean localities with favorable environ- ments. I have collected the species in the Florida Keys, at Blanqui1la Reef in the western Gulf of Mexico, Courtown Cays off Nicaragua, St. John in the Virgin Islands, and at St. Croix.

Caecum imbricatum Carpenter, 1858 Fig. 6 Caecum (ELephantulum) imbricatum Carpenter, 1858, Proc. zool. Soc. Land., 1858: 422-423. Caecum coronatum Falin, 1867, J. Conch., Paris, 15: 50-52, pI. 2, fig. 5. Caecum insigne Falin, 1867, J. Conch., Paris, 15: 52-53, pI. 2, fig. 4. Caecum formulosum Falin, 1868, Fonds de la Mer, 1; ]24-125, pI. 11, figs. 9-10 (with two varieties, paucicostata and simplex). Caecum swlptum Falin, 1881, Fonds de la Mer, 4: 15, pI. I, figs. 1-2. Caecum (ELephantanellum) imbricatum, Olsson & Harbison, 1953, Monogr. Acad. nat. Sci. Philad., No.8: 318-319, pI. 45, figs. 4, 4a, 4b. Caecum imbricatum Moore, 1970, Bull. Mar. ScL, 20(2): 371-372, fig. 1, c, d. Type-Locality.-West Indies. Here restricted to New Providence Island, in the north central Bahamas. Material.-Tague Bay: 2; Buck Island, 12 m: 2; Buck Island, 14 m: 9. It was also found in 1969 at Station 13, open sandy bottom, a few meters behind the reef at Tague Bay. Description.- The shell is of about medium thickness, and is strongly curved. Sculpture consists of both annular rings and longitudinal ridges. A weak varix is formed when growth terminates. The septum is very slightly recessed, is slightly convex, and bears a short pointed mucro. The sculpture consists of numerous weak longitudinal and axial ridges. There is a further microsculpture of numerous fine longitudi- nal striae. Specimens may be white, tan, or have a mottled pattern. A large speci- men measures 3.08 mm long, 0.46 mm in diameter at the posterior end, and 0.74 mm in diameter across the varix at the anterior end. 892 Bulletin of Marine Science [22 (4) Remarks.-C. imbricatum has also been found to be a widespread species in the western Atlantic. It is a tropical species which does not penetrate into brackish water. The depth range is considerable-about 1 to 183 m. Deeper-water specimens from off the west coast of Florida tend to be larger and to have finer sculpture than shallow-water specimens. However, there is much variation in both deep- and shallow-living material. The range of C. imbricatum includes the Bahamas, southern Florida, and the west coast of Florida as far north as Panama City.

Caecum (Meioceras) nitidum Stimpson, 1851 Fig. 11 Caecum nitidum Stimpson, 1851, Proc. Boston Soc. nat. Hist., 4: 112. Carpenter, 1858, Proc. zool. Soc. Lond., 1858: 438-439. Meioceras carpenteri Folin, 1869, AnnIs Soc. linn. Maine et Loire, 11: 8-9, fig. 3. Meioceras bitumidum Folin, 1869, Annis Soc. linn. Maine et Loire, 11: 9, fig. 4. Meioceras moreleti Folin, 1869, AnnIs Soc. linn. Maine et Loire, 11: 10, fig. 5. Meioceras deshayesi Folin, 1869, AnnIs Soc. linn. Maine et Loire, 11: 11, fig.. 6. M eioceras crossei Folin, 1869, Annis Soc. linn. Maine et Loire, 11: 11-12, fig. 7. Meioceras undulosum Folin, 1869, AnnIs Soc. linn. Maine et Loire, 11: 12, fig. 8. Meioceras coxi Folin, 1869, AnnIs Soc. linn. Maine et Loire, 11: 13, fig. 9. Meioceras subin/lexum Folin, 1869, Fonds de la Mer, 1: 165, pI. 23, fig. 8. Meioceras fischeri Folin, 1870, Fonds de la Mer, 1: 188-189, pI. 26, figs. 3-4. Meioceras imiklis Folin, 1870, Fonds de la Mer, 1: 189, pI. 26, figs. 5-6. Meioceras leoni Berillon, 1874, Fonds de la Mer, 2: 251, pI. 10, fig. 3. Meioceras cingulatum DaH, 1892, Trans. Wagner free lnst. Sci. Philad., 3(2): 302, pI. 16, figs. 6-7. Caecum (Meioceras) lermondi DaH, 1924, Nautilus, 38(1): 7-8. Meioceras apanium Woodring, 1928, PubIs Carnegie Instn, No. 385: 35I, pI. 26, figs. 11-12. Meioceras amblyoceras Woodring, 1959, Prof. Pap. U. S. Geo!. Surv., No. 306-B: 163, pI. 31, fig. 1. Type-Locality.-Florida. Here restricted to Tampa Bay, Florida. At the time C. nitidum was described, Tampa was just getting its start as a major seaport on the Florida west coast. The large bay with many shallow grassy areas was a perfect place to collect mollusks. It had been visited by many people a few years before during the Seminole War, some of whom were keenly interested in natural history. C. nitidum is a common species in the bay, and this area is a very likely one to have produced Stimpson's original specimen. 1972] Moore: Caecidae from St. Croix 893 Material.-Tague Bay: 8; Buck Island, 12 m: 3; Buck Island, 14 m: 17. It was also found at Station 10, open sandy bottom in the mound zone, in Tague Bay. This station was about two-thirds of the distance to the reef from shore. Description.- The shell is narrow at the posterior end, wider in the middle, and contracts near the aperture. The aperture is very oblique and is sometimes nearly at right angles to the main axis of the shell. The septum is slightly to moderately convex; the mucro is short and bluntly pointed. The surface of the shell is smooth. The dorsal side of the shell is moderately convex, but the ventral side does not usually have a regular curve. The middle part of the curve is only slightly concave, almost straight, or somewhat convex. Some brackish- water specimens have a well-developed ventral "hump" which can also be seen on the sides when the shell is viewed from the dorsal aspect. Other specimens from stenohaline marine environments are sometimes quite slender. The color pattern consists of irregular diffuse white spots and smaller brown spots, dashes, or curved lines. There is a great range of variation in the arrangement of the color pattern. The second stage of C. nitidum is distinctive and unlike that of any other species in the family. It forms an open spiral something like a cow horn. The first stage-the protoconch plus a portion of the te1eoconch-also shows a strong twist in the teleoconch portion. Remarks.-C. nitidum is a very successful and widespread species. It is found around Florida, the Bahamas, the Gulf of Mexico, the West Indies, and the coast of Brazil. It is a shallow-water mollusk, and is probably seldom to be found living in depths of 20 m or more. The species appears to do best in shallow bays and lagoons where the salinity remains fairly close to that of sea water. In an area such as Biscayne Bay, Florida, C. nitidum is very abundant around the bay side of the outer islands, but it is rare on the mainland side where salinities may drop to as low as 13~JO (measured November 10, 1960). C. nitidum has been a difficult species to study. The many species descriptions, the wide range of variation, and the wide geographical distri- bution all combined to keep the status of the species confused. After I had examined the types of Carpenter and Folin, I was inclined to place all except C. cubitatum in synonymy with C. nitidum. However, much more material has been collected and studied during the past several years. Sev- eral specimens, always the small cylindrical C. cornucopiae type, were found with the second stage still attached. In this species the second stage is smaller than that of C. nitidum, and is curved in only one plane or only slightly twisted. Typical C. nitidum with the cow's horn second stage are 894 Bulletin of Marine Science [22(4 )

12

FIGURES 10-12.-10, Caecum (Meioceras) cornucopiae (Carpenter), length 1.52 mm.-II, C. (Meioceras) nitidum Stimpson, length 1.88 mm.-12, C. condy- [urn Moore, length 1.04 mm, posterior end of a broken shell.

usually found in the same sample. However, C. cornucopiae Carpenter is not found in the northern Gulf of Mexico, nor in shallow bays or lagoons where the salinity fluctuates with rainfall. Material from inshore, slightly brackish water is, then, all C. nitidum. Around coral reefs and other shallow stenohaline areas, however, some of the smaller specimens of C. nitidum are difficult to separate from C. cornu- copiae. They can usually be distinguished, however, since C. cornucopiae is cylindrical with a concave ventral outline, and the color pattern is much subdued. The species is usually distinctly smaller than C. nitidum, al- though one lot from Sombrero Reef, Florida Keys, shows considerable over- lap. The color pattern is a more or less grayish white without any of the rich browns found on C. nitidum. Some specimens of C. cornucopiae show a double line of dark spots running down the dorsal side of the shell. Supposedly, C. nitidum has a very closely related ancestor in the Eocene (Bovicornu eocenense Meyer, 1886). However, Collins (1934) has shown 1972] Moore: Caecidae from St. Croix 895 that this is a pteropod, since the shell begins with a simple bulbous proto- conch. All species of Caecum have a coiled protoconch, although admit- tedly it is difficult to find an adult with the two early stages still attached. The Caecidae are found in the Western Hemisphere from the Oligocene or upper Eocene to the present. Few fossils are reported from below the Miocene, but, from the Miocene up to the present, fossils of Caecum are often abundant. C. nitidum apparently first appears in the middle Miocene of Jamaica (C. apanium Woodring) and the middle Miocene of Panama (C. ambiyoceras Woodring). C. constrictum Gabb, of about the same age from the Dominican Republic, is probably a not-quite mature C. nitidum. C. cinguiatum Dall, from the Pliocene of Florida, is the form with a strongly inflated middle. Both the ordinary form and the strongly inflated form were reported as being abundant or common in the Pliocene of St. Petersburg, Florida (Olsson et ai., 1953).

Caecum (Meioceras) cornucopiae Carpenter, 1858 Fig. 10 Meioceras cornucopiae Carpenter, 1858, Proc. zoo!. Soc. Lond., 1858: 439. Meioceras cornubovis Carpenter, 1858, Proc. zooI. Soc. Lond., 1858: 439· 440. Meioceras mariae Folin, 1881, Fonds de la Mer, 4: 15, pI. 1, figs. 5-6. Meioceras constrictum Pilsbry & Aguayo, 1933, Nautilus, 46(4): ]22-123, pI. 6, fig. 5. Meioceras bermudezi Pilsbry & Aguayo, 1934, Nautilus, 47(3): 112. Fartu/um nebu/oswn Rehder, 1943, Proc. U. S. natn Mus., 93(3161): 190- 191, pI. 20, fig. 8. Type-Locaiity.-West Indies. Here restricted to New Providence Island, in the north Central Bahamas. Material.-Tague Bay: 0; Buck Island, 12 m: 3; Buck Island, 14 m: 30. None were found behind the reef. Description.-The shell is small, slender, and cylindrical. It has a moder- ate curve, and the aperture is slightly constricted. The sides of the shell are usually slightly concave near the middle, and the aperture is only moder- ately oblique. The septum is usually somewhat convex and has a small mucro that projects very little. Surface of the shell is smooth. Color is a grayish white with small mottled clear spots in many speci- mens. Some have a double row of dark spots on the dorsal side of the shell. Sometimes the spots are light brown, but they are always small; the main color remains grayish white. The second stage of C. cornucopiae is little twisted. There is some range of variation in the length of this stage, but it never resembles a cow's horn as in C. nitidum. 896 Bulletin of Marine Science [22(4) Remarks.-Caecum cornucopiae is not a difficult species to identify in most areas. It is smaller, more slender, and with a much less oblique aper- ture than C. nitidum. Some specimens from Sombrero Reef in the Florida Keys were difficult, in part because of the poor condition of some small specimens. C. cornucopiae is a tropical stenohaline species. It is typically found around coral reefs and in back reefs or lagoons if salinity is not lowered perceptibly by freshwater runoff. C. cornucopiae was by far the most abundant microgastropod found at Serrana Bank, western Caribbean, in a study of the shelled microfauna there (Bock & Moore, 1971). This species had a general distribution at Serrana Atoll, but this is not surprising since the atoll is more than 250 km from the nearest land. Salinities remain within a very narrow range throughout the year. The type-specimens of C. cornucopiae and C. cornubovis in the British Museum are a mixed lot. Two of the types of C. cornucopiae are typical second-stage C. nitidum with broadly open spirals. It is evident from Carpenter's descriptions that he had great difficulty in separating his three species, for mostly they were based on vague characters. C. cornucopiae is now known from the Bahamas, south Florida, western Caribbean, Jamaica, Puerto Rico and Virgin Islands, and the Lesser An- tilles. It is probably a common species all around the Caribbean and lower Gulf of Mexico. It has not yet been found in the upper Gulf of Mexico, an area where C. nitidum is often abundant.

DISCUSSION St. Croix proved to be a most interesting area for small mollusks. It would be surprising that so many rare or little-known species of Caecum were found, except that most species of the are poorly known in the western Atlantic. Rare species are apparently common, once you find the environment which they prefer. One species that I looked for at St. Croix was C. insularum Moore, 1970. This species was very abundant in shallow water at Lameshur Bay, St. John. I theorized (Moore, 1970) that C. insularum had a very short pelagic larval life, and that this was the reason that it was found in a very small area. Not a single specimen has been found so far, and it appears likely that 40 km of deep water sepa- rating St. Croix from the other Virgins is an effective barrier to its dispersal. The Caecidae are seldom reported, but a list of species from St. Croix was published recently by Nowell-Usticke (1959). However, only two of the ten species listed appear to be correctly identified. Warmke & Abbott (1961) listed 10 species for Puerto Rico and the Virgin Islands, and six of these are correctly determined. The number misidentified is hardly surprising, since the Caecidae have been monographed only once, by Car- penter in 1858. This monograph, while carefully done, was published with- 1972] Moore: Caecidae from St. Croix 897 out any illustrations, and has been a source of confusion ever since. The main purpose of this paper is to clear up the confusion surrounding some of the Caribbean species. The amount of sediments making up the three deeper water samples was as follows: Tague Bay, 43 cc; Buck Island (12 m), 48 cc; Buck Island (14 m), 85 cc; or a total of 176 cc. From this were obtained 268 specimens of Caecum, and nearly 2000 specimens of other species of micromollusks. Since the other species rep- resent at least 20 families of gastropods and bivalves, it can be seen that the Caecidae are an important part of the fauna. In many shallow-water locations throughout the Caribbean the Caecidae will comprise 10 to 20 per cent or more of the micromollusks. It is obvious, then, that any stud- ies involving the ecology and distribution of small mollusks in the shallow parts of warm seas should include the Caecidae.

ACKNOWLEDGMENTS I am very grateful to Dr. H. Gray Multer for the opportunity to work on St. Croix. I am also grateful to Norman Tebble for assistance during my stay at the British Museum (Natural History), and to Dr. E. Fischer- Piette and his staff at the Laboratoire de Malacologie, Museum National d'Histoire Naturelle. Mrs. Irene Brohm helped with the photographic work. Acknowledgment is made to the donors of the Petroleum Research Fund, administered by the American Chemical Society, for partial support of this research (PRF No. 5063-AC2). This work was also supported in part by National Science Foundation Grant GB-8684.

SUMARIO NOTAS ECOL6GICAS y SISTEMATICAS SOBRE CAECIDAE DE Sr. CROIX, U. S. VIRGIN ISLANDS Se hizo una investigaci6n de la fauna marina somera en St. Croix, U. S. Virgin Islands, durante los vera nos de 1969 y 1970. Mediante bucea se colectaron muestras de sedimentos y de ellas se escogieron los micromo- luscos. Los Caecidae fueron estudiados en sedimentos de bahlas someras y se hizo un estudio cuantitativo en tres estaciones ligeramente mas pro- fund as en y alrededor de los arrecifes de coral. Siete especies de Caecidae, 268 ejemplares, fueron encontrados en 176 cc de sedimento de las tres estaciones en aguas mas profundas. Una octava especie fue rara en el area de agua mas somera. Las ocho especies: Caecum condylum Moore, C. subvolutum Folin, C. lineicinctum Folin, C. regulare Carpenter, C. textile Folin, C. imbricatum Carpenter, C. (Mioceras) nitidum Stimpson y C. (M.) cornucopiae (Car- penter), son todas poco conocidas. Las primeras tres especies no viven 898 Bulletin of Marine Science [22(4) en arrecifes traseros 0 areas lagunosas y por ello se les supuso extremada- mente raras. Sin embargo, estas tres especies comprendieron el 55 por ciento de los Caecidae de las tres estaciones en aguas mas profundas. Viven en un ambiente que ha sido muestreado poco, por ello han sido raramente colectadas. La distribuci6n para todas las especies es tropical, aunque C. nitidum y C. imbricatum son encontradas tambien en la parte norte del Golfo de Mexico.

LITERATURE CITED BERILLON, M. 1874. Chapter 31, Cotes du Mexique (Pacifique et mer des Antilles), in Folin, Leopold de, Les Fonds de la Mer, 2: 247-251, pl. 10, fig. 3. BOCK, W. D. AND D. R. MOORE 1971. The foraminifers and micromollusks of Hogsty Reef and Serrana Bank and their paleoecological significance. Proc. 5th Caribb. geol. ConL: 143-146, 2 figs. CARPENTER, PHILIP P. 1858. First steps towards a monograph of the Caecidae, a family of rostrif- erous Oasteropoda. Proc. zooI. Soc. Lond., 1858: 413-444. COLLINS, R. L. 1934. A monograph of the American Tertiary pteropod mollusks. Johns Hopkins Univ. Stud. Oeo!., No. 11: 137-234, pis. 7-14. DALL, W. H. 1892. Contributions to the Tertiary fauna of F]orida. Trans. Wagner free lnst. Sci. Philad., 3(2): 201-473, pis. 13-22. 1924. A remarkable caecid from F]orida. Nauti]us, 38: 7-8. FOLlN, LEOPOLD DE 1867. Descriptions d'especes nouvelles de Caecidae. J. Conch., Paris, 15: 44-58, pIs. 2-3. 1867- 1887. Les Fonds de la mer. Paris, 4 vo]s., 1258 pp., 57 pis. 1869. Le genre Meioceras. Ann]s Soc. linn. Maine et Loire, 11: 1-15, 1 pI. 1879. On the of the H.M.S. Challenger Expedition. The Caeci- dae, comprising the genera , Watsonia, and Caecum. Proc. zool. Soc. Lond., 1879: 806-812. KISCH, B. S. 1959. La collection de Caecidae du Marquis de Fo]in en Museum Nationa] d'Histoire Naturelle. J. Conch., Paris, 99(1): 15-42. MEYER, O. 1886. Contributions to the Eocene paleontology of A]abama and Missis- sippi. Bull. geol. Surv. A]a., No.1 (2): 63-85, 3 pis. MOORE, D. R. 1969. A new Caecum from the tropical western At]antic. Nauti]us, 83( I) : 26-28. 1970. A new Caecum from Puerto Rico and the Virgin Is]ands. Bu]l. Mar. Sci., 20(2): 368-373, 2 figs. MOORE, H. F. 1923. Commercial Sponges. Pp. 668-691, figs. 240-251, in Tressler, D. K. (Ed.), Marine products of commerce. Reinho]d Publishing Corp., New York, 762 pp. 1972] Moore: Caecidae from St. Croix 899

NOWELL-USTICKE, G. W. 1959. A check list of the marine shells of St. Croix, U. S. Virgin Islands, with random annotations. Burlington, Vermont, vi + 90 pp., 4 pIs. OLSSON, A. A. AND A. HARBISON 1953. Pliocene Mollusca of southern Florida with special reference to those from north St. Petersburg. Monogr. Acad. nat. Sci. Philad., No.8: 1-457, pIs. 1-65. PILSBRY, H. A. AND C. G. AGUAYO 1933. Marine and freshwater mollusks new to the fauna of Cuba. Nautilus, 46(4): 116-123. 1934. Meioceras bermudezi, new name for M. constrictum P. and A. Nau- tilus, 47 (3); 112. REHDER, H. A. 1943. New marine mollusks from the Antillean region. Proc. U. S. natn. Mus., 93(3161): ]87-203, pIs. ]9-20. STIMPSON, W. 1851. Monograph of the genus Caecum in the United States. Proc. Boston Soc. nat. Rist., 4: 112-113. WARMKE, G. LAND R. T. ABBOTT 1961. Caribbean Seashells. Livingston Publishing Co., Narberth, Pennsyl- vania, x + 346 pp., 44 pIs., 34 figs., 19 maps. WOODRING, W. P. 1928. Miocene mollusks from Bowden, Jamaica. Pt. 2. Gastropods and discussion of results. PubIs Carnegie Instn, No. 385: 1-564, pIs. 1-40. 1959. Geology and paleontology of Canal Zone and adjoining parts of Panama. Description of Tertiary mollusks. (Gastropods: Vermeti- dae to Thaididae). Prof. Pap. U. S. geol. Surv., No. 306-B: 147-239, pIs. 24-38.