Stygologia 2 (112) 1986, E. J. Brill, Leiden

MESOZOIC RELICTS IN MARINE CAVES OF

RAYMOND B. MANNING ') C. W. HART, JR.') & T. M. ILIFFE2)

SUMMARY Evidence is presented supporting the hypothesis that some of the invertebrates inhabiting marine caves in Bermuda and the Caribbean may have invaded those systems before the opening of the North Atlantic in the Jurassic. It is suggested that the cave havitats provide a potential con- tinuum of habitats from the deep-sea to above sea level fresh waters, and that these habitats could have been entered anywhere in the water column.

On prCsente des donntes B l'appui de I'hypothbse que certains des inverttbrhs habitant des grot- tes marines aux Bermudes et dans les Caraibes auraient pu envahir ces systbmes avant l'ouver- ture de 1'Atlantique Nord au Jurassique. On suggbre que le domaine des grottes fournit un con- tinuum potentiel d'habitats, depuis les eaux abyssales jusqu'aux eaux douces au-dessus du niveau de la mer, et que ces habitats ont CtC abordables pour la faune B n'importe quel endroit de la colonne d'eau.

INTRODUCTION In recent years there has been a marked increase in studies of the occur- rence, biology, and distribution of invertebrates, especially , that are found in anchialine pools and marine caves. These include a variety of groundwater habitats in rock, occurring primarily on oceanic islands. One aspect of the findings of these and related, earlier studies has been the puzzling and often inexplicable distribution patterns of some of these crustaceans: the caridean Procaris occurring on in the south Atlantic (Chace & Manning, 1972) and later discovered in Hawaii (Holthuis, 1973); other from a limestone fissure that recently opened in the southern Sinai as well as from pools on Hawaii and elsewhere (Holthuis, 1973); the subsequent discovery of one of the genera of these shrimps, Calliasmata, in the Dominican ReP ublic (Chace, 1975); the occurrence of a species of Munidopsis, a deep-water galatheid genus, from a recently formed

I) Department of Invertebrate Zoology, National Museum of Natural History, Smithsonian In- stitution, Washington, DC 20560, U.S.A. 2, Bermuda Biological Station, Ferry Reach 1-15, Bermuda. lava tube in the (Wilkens & Parzefall, 1974); the class Remipedia, described from a limestone cave in the Bahamas (Yager, 1981) and later found in the same lava tube containing Munidopsis in the Canary Islands (Iliffe, Wilkens, Parzefall & Williams, 1984); the occurrence of a genus of subterranean mysids, Stygiomysis, in southern Italy and in caves in the Bahamas and the Caribbean (Bowman, 1976; Bowman, Iliffe & Yager, 1984); and the distribution of a genus of subterranean amphipods, Pseudoniphargus, found around the Mediterranean Basin and some eastern Atlantic islands (Stock, 1980) and in Bermuda (Sket & Iliffe, 1980). There are many other examples of such distribution patterns in the literature. Unlike the shrimps and the galatheid, many of these lack distributive larval stages. In a review of the biology of anchialine shrimps from the Indo-West Pacific, Maciolek (1983: 115) commented that "most if not all of these hypogeal shrimps could have widespread and possibly longstanding populations in submerged as well as emergent rock of the tropical Indo-Pacific," and (1983: 116) "This broadened habitat hypothesis allows that the shrimps could occur in the groundwaters of many isolated and archipelagic islands where they have not yet been found, in shallow reefs and seamounts, and possibly in suitable rock of continental shelves." Longstanding is a key word, groundwater is another. We also had come to a similar conclusion, that some of the crustaceans oc- curring in caves and groundwaters in the Caribbean had been in those habitats before the Tertiary, and that some were closely tied to the deep sea (Iliffe, Hart & Manning, 1983). The occurrence of these animals in Pleistocene limestone rock of fairly recent origin tends to obscure the possibility that these organisms could have inhabited these groundwater habitats for millions of years. Using the term "cave" for these habitats on Bermuda and elsewhere is misleading, for there are not only subterranean caverns but also more widespread flooded interstices in the rock, interconnected with the caverns. Elsewhere (Hart, Manning & Iliffe, 1985) we have suggested that the term crevicular be used for these groundwater habitats in rock. These habitats may occur at the surface in the limestone cap, where the inhabitants are most often encountered because of limitations in sampling methodologies, and the habitats may also occur anywhere on the submerged surfaces of the volcanic pedestals that attach oceanic islands to the sea bed. Subterranean habitats are undoubtedly present in submerged oceanic ridges and other undersea features, including sea mounts. These habitats can be entered anywhere in the water column, providing direct access to habitats with environmental conditions similar to those found in the deep sea. Once invaded, all interconnecting habitats within the rock, including those above sea level in fresh water, are open to the colonizers. Thus habitats ranging from seeps to underground caverns to exposed anchialine pools to fresh water wells are available to 158 BERMUDA MARINE CA VE SYMPOSIUM

members of this fauna. There are also potential direct connections between marine crevicular habitats with the oceanic water of the abyss.

BACKGROUND The following information is from Sket & Iliffe (1980), who summarized in- formation on Bermuda's marine caves and provided preliminary findings on the cave fauna. About 150 marine caves are known from the Bermuda Islands. They are situated in a limestone cap of Pleistocene age overlying a volcanic platform that is now about 75 meters below present sea level. The island was formed by volcanic activity on the Mid-Atlantic Ridge in the late Cretaceous, about 110 million years ago. At that time the island was closest to the Euro- pean land mass. Although Bermuda has never been part of the North American land mass, it apparently drifted westward from the Mid-Atlantic Ridge with the North American Plate. Because the caves of Bermuda, the Bahamas, and other islands in the Caribbean are generally of Pleistocene age, those studying their fauna generally have sought explanations as to how cave colonization might have occurred in fairly recent times. We suggest that the origins of Bermuda's cave fauna are less closely related to the origin of the caves than to the origin of Bermuda itself in the Cretaceous. We believe that the largely puzzling distribution patterns of crevicular orgnanisms that lack pelagic larvae might best be explained by the thesis that at least some elements of the fauna of marine caves in Bermuda and elsewhere in the Atlantic are Mesozoic relicts that colonized crevicular habitats in rock along the Mid-Atlantic Ridge as the continents separated. These would not be the first examples of Mesozoic relicts associated with a submerged oceanic ridge. Newman (1979) described a scalpellid barnacle from the East Pacific Rise and considered it to be a Mesozoic relict. Bermuda today is near the winter isotherm of 20°C; it has the northernmost extension of coral reefs in the west Atlantic. As Briggs (1974: 61) commented, "nowhere else in the world does a tropical fauna occur at such a high latitude (32"15')." However, during winter, the sea surface temperature may drop to as low as 15°C. During Pleistocene glacial periods, the sea surface temperature was lowered by as much as 6" to 9°C (Briggs, 1966), enough to have caused of at least some shallow water tropical taxa. Briggs (1966, 1970) has pointed out that various studies have demonstrated that the North Atlantic shallow water fauna has undergone a general "depauperization," and that the as well as other North Atlantic islands have a very low level of endemism. This is probably the result of mass extinctions due to cooling of sea surface temperatures during glacial periods. Iliffe, Hart & Manning (1983) noted that the levels of endemism of Ber- muda's cave fauna (30%) are considerably higher than endemism among lit- toral species (2% for the decapods; Markham & McDermott, 1980). They fur- ther suggested (1983: 141) that some of Bermuda's cave species represented STYGOLOGIA 2 (112) 1986

"groups that survived on submergent and emergent sea mounts along the Mid-Atlantic Ridge since the middle Mesozoic," while other species in the caves were related to the fauna of the deep-sea. Even though inshore surface water temperatures around Bermuda may fluc- tuate between 15°C in winter to more than 30°C in summer, within the caves, at depths below three meters or so, the water temperature remains relatively constant, all year, at about 20.5"C (lliffe, Hart & Manning, 1983), suggesting the possibility of geothermal heating. If the deeper waters of the caves re- mained at relatively higher temperatures during the Pleistocene glacial periods, the caves could have served as warm thermal refuges through the periods of reduced sea temperature. Sket & Iliffe (1980) summarized information on the fauna of marine caves in Bermuda and reported that the caves were inhabited by a wide variety of marine invertebrates. In all, they reported the discovery of more than 50 species, representing groups from the ciliates to tunicates. In discussing the zoogeographical affinities of the cave fauna, they pointed out some obvious af- finities of some of the species with east American and Caribbean species. They also noted (1980: 878) that "Less expected were some striking zoogeographical connections of Bermuda to the east." They suggested and rejected four theories that might explain some of the distribution patterns of the animals found in Bermudan caves: , stranding of species on the shorelines of receding fossil seas, connections with the abyssal fauna, and drift- ing in the open ocean. They concluded (1980: 879) that "it is far from clear what zoogeographical connections existed or what dispersal processes were operative in producing Bermuda's cave fauna," and "Once species had I reached Bermuda, it was still necessary for them to invade the cave systems." Subsequently, we (Iliffe, Hart & Manning, 1983) suggested that some of Ber- muda's cavernicolous marine fauna originated from stocks transported from the Caribbean by the Gulf Stream; some are relict faunal elements from the deep-sea region; some possibly are Tethyan relicts; and some represent groups that have survived on submerged undersea features as well as emergent sea mounts along the Mid-Atlantic Ridge since the Middle Mesozoic. In another paper we document ties of the cave faua to the fauna of the deep-sea (Hart, Manning & Iliffe, 1985). Here we provide additional evidence for the hypothesis that at least some of the faunal elements in marine caves in Ber- muda, and possibly elsewhere in the Caribbean, may have entered the ground- waters of the islands while the precursors of the islands were still on or adjacent to the Mid-Atlantic Ridge. We consider some of these faunal elements to be Mesozoic relicts.

CAVE SHRIMPS Hart & Manning (1981) first recorded the occurrence of four species of cari- bean shrimps from cave habitats in Bermuda. The most common of these is 160 BERMUDA MARINE CA VE SYMPOSIUM

Barbouria cubensis (von Martens), then known from caves in Cuba, the Bahamas, and Cayman Brac (Hobbs, Hobbs & Daniel, 1977). Barbouria and four closely related monotypic genera (Manning & Hart, 1984) do not conform to the longitudinal gradient in distribution patterns shown by Abele (1982) to be common in a wide variety of crustacean groups, ranging from myodocopid ostracodes to decapods. Most groups are represented by the largest number of species in the Indo-West Pacific region, followed by the western Atlantic, then by either the eastern Atlantic or the eastern Pacific. In Barbouria and its allies, two species occur in the Indo-West Pacific, one shallow, one bathyal, and that deep-water species, Ligur ens$iis, also occurs in the Mediterranean and on both sides of the Atlantic. The largest number of genera and species, four, are found in the western Atlantic. As has been observed in some other groups of crevicular organisms, one component of the group lives in the deep-sea, whereas other components occur in anchialine or cave habitats. Another example of this is the galatheid genus Munidopsis, with one species in a cave in the Canary Islands, many species free- living in outer shelf, slope, and abyssal depths (Doflein & Balss, 1913). A polynoid polychaete worm, Gesiella jameensis Hartmann-Schroder, representing a group otherwise composed of deep-sea species (Pettibone, 1976), also occurs in that same cave in the Canary Islands. Because the caves in Bermuda and probably elsewhere comprise crevicular habitats in rock that potentially extend from the sea surface to the abyss, these habitats could have been entered anywhere in the water column. Deep-sea groups may well have been able to enter the caves directly, thus explaining why so many different deep-sea groups are represented in the cave faunas. Since 1981 we have collected several other species of decapods in Bermuda's caves. One of these is a single specimen of the anchialine shrimp genus Procaris, found in an extensive marine cave. This genus is otherwise known from two species taken in similar anchialine habitats, exposed pools in lava flows, one from Ascension Island (Chace & Manning, 1972) and one from Hawaii (Holthuis, 1973). This shrimp and the Bermudan Typhlatya il~ffeiHart & Man- ning, the latter morphologically closer to a species from Ascension Island than to any of the several species known from subterranean fresh water habitats in the West Indies and Mexico (Hobbs, Hobbs, & Daniel, 1977), suggest a com- mon origin for the species of Procaris and Typhlatya now known from very dif- ferent islands: Ascension, with an estimated age of 1-2 million years and an- chialine habitats in lava, and Bermuda, formed more than 100 million years ago, with cave habitats in limestone. The islands share one characteristic: both originated on the Mid-Atlantic Ridge. Hobbs & Hart (1982) recently reviewed the freshwater epigean shrimps of the genus Atya, a genus restricted to the Americas and West Africa. They found that two species, A. gabonensis Giebel and A. scabra (Leach), were iden- tical from localities on both sides of the Atlantic, and that two other species, A. intmdia Bouvier from Africa and A. innocous (Herbst) from the Americas, were so closely related that they were reluctant to recognize them as different species. They noted (1982: 22) "Thus these three shrimps [A. gabonensis, A. in- termedia, and A. scabra] have identical or such close counterparts in the Americas that they must be considered little, if any, changed since the Africa- America continental masses were approximate." They also pointed out (p. 20) that "The progenitors of modern Atya with little doubt existed as recognizable members of the genus by the late Mesozoic (probably by early Jurassic times)." Monod (1975) figured the distribution of present atyid genera in the Triassic. The age of the atyids, the ability of Typhlatya and Procaris to utilize crevicular habitats in rock, and the origin of both Ascension Island and Bermuda on the Mid-Atlantic Ridge provide some clues as to how Typhlatya colonized both Ascension and Bermuda, and, probably, the Caribbean islands as well. The species of Typhlatya all live in subterranean or anchialine habitats, with most species known from crevicular habitats in the Caribbean (Hobbs, Hobbs, & Daniel, 1977) (fig. 1). The species from Ascension and Bermuda, which are closer to each other morphologically than to the other species in the genus, also are the only two Atlantic species known to live in salt water. If we assume that the precursors of modern Typhlatya frequented crevicular habitats along the Mid-Atlantic Ridge while the continents were approx- imated, it is relatively easy to derive the present species of Typhlatya from such a salt water ancestor or ancestors. It is far harder to derive the salt water species of the genus on Ascension and Bermuda from fresh water ancestors in the Caribbean, especially since there is no evidence that the larval stages of the freshwater species require or are even able to spend any time in salt or brackish water. A similar scenario could explain the puzzling distribution of the two popula- tions of Procaris in the Atlantic. Although now known from two seemingly dif- ferent kinds of habitats on two very different and widely separate islands in the Atlantic, they may well live in crevicular habitats in rock if other conditions are favorable. It is easier to derive the species known today from precursors that lived along the Mid-Atlantic Ridge than from supposed pelagic larvae of ancestral forms.

OTHER CAVE CRUSTACEANS Sket & Iliffe (1980: 878) noted that the subterranean amphipod genus Pseudoniphargus, represented by undescribed species in Bermuda's marine caves, is widely distributed in the Mediterranean belt, the Iberian Peninsula and is known from the Azores and Madeira as well (fig. 2). They commented that "It is a quite ubiquitous subterranean , living in caves and in- terstitial waters, at marine salinities and in fresh water." Stock (1980: 105) 162 BERMUDA MARINE CA VE SYMPOSIUM

Fig. 1. Distribution of Procaris and Typhlatya in the Atlantic and the Americas. reviewed the species of Pseudoniphargus and noted: "The evolution of Pseudoniphargus - the development of inhabitants of inland waters from marine ancestors - is discussed at some length. It is likely that this evolution is of the regression model type: stranding of marine populations during sea-level regressions. " Stock further noted "Several authors . .. have emphasized the probability that populations of littoral or shallow-water animals, more in par- ticular the inhabitants of interstitia of macroporous substrates, stranded because of various marine regressions in the Mediterranean region during the Tertiary epoch. These stranded populations got gradually adapted to the con- ditions of more continental waters and are now distributed in land areas that were previously submerged. " Whereas the method suggested by Stock is one of the ways marine organisms could have colonized the cave habitats, we suspect that it may be more likely that the precursor of Pseudoniphargus invaded subterranean waters long before the continents separated, and that members of that genus inhabiting oceanic islands colonized those islands before they drifted away from the Mid-Atlantic Ridge in the Middle Jurassic, while the Atlantic was still closed (see maps in Sclater et al., 1977). This has been suggested by Magniez (1978: 27; 1981 : 78) STYGOLOGIA 2 (112) 1986 163

Fig. 2. Distribution of Pscudoniphargur and Stygiomysis.

for the stenasellids, exclusively limnic subterranean isopods with populations in Europe and Texas and Mexico, and, earlier, was suggested by Schellenberg (1939: 300) for Pseudoniphargus. The mysid genus Stygomysis (Fig. 2) also provides an example of a subterra- nean group which may have colonized subterranean waters before the con- tinents separated. It comprises one species in the Mediterranean, S. hydruntina Caroli, and three in the Caribbean: S. holthuisi (Gordon) from St. Martin and Puerto Rico (Bowman, 1976), (Botosaneanu, 1980), and Grand Bahama Island owma man, Iliffe & Yager, 1984); S. major Bowman from Jamaica (Bowman, 1976); and S. clarkei Bowman, Iliffe, and Yager from the Caicos Islands (Bowman, Iliffe & Yager, 1984). T. E. Bowman (pers. comm.) suggests that the genus is very primitive and possibly very old. The amphipods and the mysids lack pelagic larvae, and thus lack distributive stages, have members that exhibit adaptive changes for an ex- istence in caves, and show distribution patterns that might best be explained by assuming that populations already were established in subterranean habitats before the continents separated in the Jurassic. Poulson (1971) has commented on the similarities of habitats in the deep sea and in caves - among the characteristics shared by both environments is that are old, climatically stable, and non-rigorous. Sterrer (1973), in discussing continental drift as a dispersal mechanism for meiobenthic organisms, pointed out one characteristic that would be shared by cave or groundwater organisms. Unlike many other kinds of isolating mechanisms, separation of populations by continental drift would not disrupt or change the habitat, and thus there would be less selective pressure for change. Thus it is not surprising that some marine cave crustaceans from both sides of the Atlantic are identical at the generic level. Indeed, there are some suggestions that this pattern of dispersal may not be restricted to subterranean organisms. Newman & Ross (1977) described a bar- nacle, Tesseropora atlantica, from shore localities in Bermuda and the Azores. The group of barnacles to which this species belongs lacks nauplii larvae, the young being released as cyprids; thus this group lacks the distributive stages characteristic of many barnacles. This species subsequently was found at St. Peter and Paul's rocks, in the south Atlantic (W. A. Newman, pers. comm.). This could well be an example of a littoral species that colonized oceanic islands while those islands were adjacent to or part of the Mid-Atlantic Ridge. Newman & Ross (1977: 207) noted that this species provided additional evidence that oceanic islands can act as refugia for ancient forms.

ACKNOWLEDGEMENTS This paper is an expanded version of a paper presented by us (Hart, Iliffe, & Manning, 1983) at a contributed paper session sponsored by The Crustacean Society and the Association of Southeastern Biologists at the ASB meeting in Lafayette, Louisiana, in April 1983 and at a sym- posium, Biogeography of the Crustacea, sponsored by The Crustacean Society and the American Society of Zoologists at their annual meeting in Philadelphia in December 1983. We thank Rodney M. Feldmann, Robert H. Gore, Kenneth L. Heck, and three anonymous reviewers for their critical reviews of various drafts of the manuscript. Our work on the cave fauna of Bermuda has been supported by grants from the National Geographic Society (grant no. 2485-82), the Scholarly Studies Program and the Secretary's Fluid Research Fund, , and National Science Foundation grant BSR 8215672.

REFERENCES ABELE,L. G., 1982. Biogeography: 242-304. In: L. G. ABELE,ed., Systematics, the fossil re- cord, and biogeography. The Biology of Crustacea, 1. (Academic Press, New York). BOTOSANEANU,L., 1980. Stygiomysis ho!thuisi found on Anguilla (Crustacea: Mysidacea). Stud. Fauna Curacao, 61(190): 128-132. BOWMAN,T. E., 1976. Stygiomysis major, a new troglobitic mysid from Jamaica, and extension of the range of S. holthuisi to Puerto Rico (Crustacea: Mysidacea: Stygiomysidae). Int. J. Speleol., 8:365-373. BOWMAN,T. E., T. M. ILIFFE& J. YACER,1984. New records of the troglobitic mysid genus Sty- giomysis: S. clarkei, new species, from the Caicos Islands, and S. holthuisi (Gordon) from Grand Bahama Island (Crustacea.. Mysidacea)., Proc. biol. Soc. Washington,., . 97:637-644. BRIGCS,J. C., 1966. Oceanic islands, endemism, and marine paleotemperatures. Syst. Zool., 15:153-163. STYGOLOGZA 2 (112) 1986

-- , 1970. A faunal history of the North . Syst. Zool., 19:19-34. --, 1974. Marine Zoogeography. (McGraw-Hill, New York). CHACE,F. A,, JR., 1975. Cave shrimps (: ) from the Dominican Republic. Proc. biol. Soc. Washington, 88: 29-44. CHACE,F. A., JR. & R. B. MANNING,1972. Two new caridean shrimps, one representing a new family, from marine pools on Ascension Island (Cmstacea: Decapoda: Natantia). Smith- sonian Contrib. Zool., 131: 1-18. DOFLEIN,F. & H. BALSS,Die Galatheiden der Deutschen Tiefsee-Expedition. Wiss. Ergebn. Dt. Tiefsee-Exped. "Valdivia", 20:125-184. HART,C. W., JR., T. M. ILIFFE& R. B. MANNING,1983. The caves of Bermuda: Biogeogra- phical anomalies. ASB Bull., 30:61 [abstract]. HART,C. W., JR., R. B. MANNING& T. M. ILIFFE,1985. The fauna of Atlantic marine caves: evidence of dispersal by sea floor spreading while maintaining ties to the abyss. Proc. biol. Soc. Washington, 98:288-292. HART,C. W., JR & R. B. MANNING,1981. The cavernicolous caridean shrimps of Bermuda (Alpheidae, Hipppolytidae, and Atyidae). J. Crust. Biol., 1:441-456. HOBBS,H. H., Jr. & C. W. HART,Jr., 1982. The shrimp genus Atya (Decapoda: Atyidae). Smithsonian Contrib. Zool., 364:iii + 143. HOBBS,H. H., JR., H. H. HOBBS111, & M. A. DANIEL,1977. A review of the troglobitic deca- pod crustaceans of the Americas. Smithsonian Contrib. Zool., 244:v + 183 pages. HOLTHUIS,L. B., 1973. Caridean shrimps found in land-locked saltwater pools at four Indo- West Pacific localities (Sinai Peninsula, Funafuti Atoll, Maui and Hawaii Islands), with the description of one new genus and four new species. Zool. Verhand., Leiden, 128:l-48. ILIFFE,T. M., C. W. HART,JR. & R. B. MANNING,1983. Biogeography and the caves of Ber- muda. Nature, 302: 141-142. ILIFFE,T. M., H. WILKENS,J. PARZEFALL& D. WILLIAMS,1984. Marine lava cave fauna: Composition, biogeography, and origins. Science, 225: 309-311. MACIOLEK,J. A., 1983. Distribution and biology of Indo-Pacific insular hypogeal shrimps. Bull. mar. Sci., 33:606-618. MAGNIEZ,G., 1978. Quelques probltmes biogkographiques, tcologiques et biologiques de la vie souterraine. Bull. sci. Bourgogne, 31:21-35. --, 1981. Biogeographical and paleobiogeographical problems in stenasellids (Crustacea Isopoda Asellota of underground waters). Int. J. Speleol., 11:71-81. MANNING,R. B. & C. W. HART,JR., 1984. The status of the hippolytid shrimp genera Barbouria and Ligur (Cmstacea: Decapoda): a reevaluation. Proc. biol. Soc. Washington, 97:655-665. MARKHAM,J. C. & J. J. MCDERMOTT,1981. A tabulation of the Cmstacea Decapoda of Ber- muda. Proc. biol. Soc. Washington, 93: 1266-1276. MONOD,Th., 1975. Sur la distribution de quelques Crustacts malacostracts d'eau douce ou saumltre. MCm. Mus. natn. Hist. nat., Paris, (A) (Zool.) 88:98-105. NEWMAN,W. A., 1979. A new scalpellid (Cirripedia); a Mesozoic relic living near an abyssal hydrothermal spring. Trans. San Diego Soc. nat. Hist., 19: 153-167. NEWMAN,W. A. & A. ROSS,1977. A living Tesseropora (Cirripedia: Balanomorpha) from Ber- muda and the Azores: first records from the Atlantic since the Oligocene. Trans. San Diego Soc. nat. Hist., 18:207-216. PETTIBONE,M. H., 1976. Revision of the genus Macellicephala McIntosh and the subfamily Macellicephalinae Hartmann-Schrder (Polychaeta: Polynoidae). Smithsonian Contrib. Zool., 229:iv + 71. POULSON,T. L., 1971. Biology of cave and deep sea organisms: a comparison. Bull. natn. Spe- leol. Soc., 33:51-61. SCHELLENBERG,A., 1939. Verbreitung und Alter der Amphipoden-Gattung Pseudoniphargus nebst Verbreitung der Gattung Niphargus. Zool. Anz., 127:297-304. SCLATER,J. G., S. HELLINGER& C. TAPSCOTT,1977. The paleobathymetry of the Atlantic Ocean from the Jurassic to the present. J. Geology, 85:509-552. SKET,B. & T. M. ILIFFE,1980. Cave fauna of Bermuda. Int. Revue ges. Hydrobiol., 65:871-882. STERRER,W., 1973. Plate tectonics as a mechanism for dispersal and speciation in inter- stitial sand fauna. Netherlands J. Sea Res., 7:200-222. 166 BERMUDA MARINE CA VE SYMPOSIUM

STOCK,J. H., 1980. Regression model evolution as exemplified by the genus Pseudoniphargus (Amphipoda). Bijdr. Dierk. 50:105-144. WILKENS,H. & J. PARZEFALL,1974. Die Oekologie der Jameos del Agua (Lanzarote). Zur Ent- wicklung limnischer Hoehlentiere aus marinen Vorfahren. Ann. Sptltol., 29:419-434. YAGER,J., 1981. Remipedia, a new class of Cmstacea from a marine cave in the Bahamas. J. Crust. Biol., 1:328-333. 1

Received: 22 January 1985