EARLY PLEISTOCENE FRESHWATER BIVALVES (MOLLUSCA:UNIONIDAE) FROM THE LEISEY SHELL PITS, HILLSBOROUGH COUNTY, FLORIDA Arthur E. Bogan i and Roger W. Porte112 ABSTRACT Unionid valves are reported from the early Pleistocene Bermont Formation at the Izisey Shell Pits, Hillsborough County, Florida. Collected from the base of Leisey Shell Pit 3 were numerous valves of Utterbackia sp. cf. U. imbecillis (Say 1%29) and Megalonaias boykiniana (Lea 1840) and fromthebase of Leisey Shell Pit 1 several valves of EUiptoideus sloationus (Lea 1840) were collected. A matched pair of Megalonaias valves was also obtained from spoil at Leisey Shell Pit 1 and is most likely from the same horizon as the EUiptoideus. These southern Florida unionid remains represent the oldest Cenozoic freshwater bivalve fauna in the eastern United States. The fossil occurrence of Megalonaias and Elliproideus, 320 kilometers south of their modern range limit in the panhandle of Florida points to a major range contraction ofthese unionid species in peninsular Florida since the Pleistocene. RESUMEN Se reportan valvas unionidas provenientes de la formaci6n de Bermont del Pleistoceno temprano en los dep6sitos de conchuelas de Leisey, en el condado de Hillborough, Florida. Se colectaron numerosas valvas de Unerbackia sp. d U. imbeciths (Say 1829) y de Megalona,as boykiniana (Lea 1840) desde la base del dep6sito de conchuelas de Leisey 3. Adicionalmente, se colectaron varias valvas de EUiptoideus sloatianus (Lea 1840) desde la base del deposito de conchuelas de Leisey 1. Tambi6n se obtuvo un par concordante de valvas de Megalonaias desde desechos en el dep6sito de conchuelas de Leisey 1, y muy probablemente desde el mismo horizonte que EUiptoideus. Estos restos unionideos del mir de Florida representan la fauna mas antigua de vivalvos de agua dulce del Cenozoico del Este de los Estados Unidos. La ocurrencia f6sil de Megalonaias y EUiptoideus 320 km inds al sur que su rango actual en Florida no peninsular, sefiala una gran contracci6n durante el Pleistoceno en la distribuci6n de estas especies unionideas en Florida peninsular. 1 The senior author is Director of Freshwater Molluscan Research. 36 Venus Way, Sewell NJ 08086, U.SA 2 The junior author is the Senior Biological Scientist and Collection Manager of Invertebrate Paleontology, Florida Museum ofNatural History. University of Florida, P. 0. Box 117800, Gainesville, FL 32611-7800, U.SA BOGAN, A E., and K W. PORTELL 1995. Early Pleistocene Freshwater Bivalves (Mollusca:Unionidae) from the Leisey Shell Pits, Hillsborough County, Florida. Bull. Florida Mus. Nat Hist 37 PL 1(6):165-176. 166 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, VT. I, No. 6 INTRODUCTION The unionid fossil record of the eastern United States is rather limited. Evidence of freshwater bivalves is primarily restricted to late Pleistocene (Wisconsinan) deposits (Henderson 1935; Modell 1957; Bogan and Grady 1991). Two reported unionid faunas support the ancient history of the diversity of freshwater bivalves in the eastern United States. One of these, the Fishhouse Local Fauna from New Jersey, is represented by 12 described species (Kat 1983; Bogan et al. 1989) and dates to about 125,000 YBP. The taxa recognized in this fauna are only a portion of those expected from an historic Atlantic Slope freshwater fauna. The other Pleistocene freshwater bivalve fauna is from Hamilton Cave, West Virginia, located on the headwaters of the Potomac River. On the basis of microtine rodent species, the Hamilton Cave deposits were dated from between 740,000 and 850,000 YBP ([rvingtonian ID (Bogan and Grady 1991). This fauna includes at least four species of unionids, all of which are found in the area today with one genus possibly having a more southern modern distribution. Other Pleistocene records of unionids from along the Atlantic Coast are of isolated valves (Bogan and Grady 1991). Two species, Elliptic caloosaensis (Dall 1898) and Elliptio pachyodon Pilsbry 1953, have been described from older deposits (Pliocene) of southern Florida but are not considered to represent faunas. Each species was collected separately and no other freshwater bivalves were associated. Two Texas faunas older than the Leisey fauna are known from the Pliocene Reynosa Formation (Marshall 1929) and the late Miocene Catahoula Sandstone (MacNeil 1935). The purpose of this paper is to document the occurrence of the oldest unionid fauna in the eastern United States. Four identifiable freshwater bivalve taxa were collected from the Leisey Shell Pits, located on the southeast edge of Tampa Bay, Hillsborough County, Florida (Wl/2, Sec. 15, T32S, R18E, Ruskin Quadrangle, USGS 7.5 minute series; Fig. 1). Most specimens were collected from freshwater exposures at the base of the lowermost marine shell unit at Leisey Shell Pits 1 and 3 (Fig. 2). On.the basis of the marine molluscan fauna, Hulbert and Morgan (1989) placed this lowermost shell bed (lower shell bed of Portell et al., this volume) in the early Pleistocene Bermont Formation. ACKNOWLEDGMENTS Kevin S. Schindler and Gary S. Morgan, formerly ofthe Florida Museum ofNatural History, and Frank A Garcia, Ruskin, Florida, are gratefully thanked for collecting some ofthe specimens discussed here. Fred G. Thompson and Kurt Auffenber& Florida Museum of Natural History, provided encouragement and suggestions. Carter R. Gilbert Florida Museum of Natural History, patiently answered questions on the zoogeography ofthe freshwater fishes of the west coast of Florida William G. Lyons, Florida Depailment of Natural Resources, St. Petersburg, Florida discussed the definition of the Be,mont Formation and kindly BOGAN & PORTELL: FRESHWATER BIVALVES FROM LEISEY SHELL PIT 167 0 A r | HILLSBOROUGH COUNTY LEISEY SHELL PITS ..0 0 RUSKINB TAMPA BAY - r erp<1*&40 COO~~0~OUMY RO~ MAYES BAYOU ACH SUN CITY-- BAY T 0 '= Figure 1. (A) General location map of the Ikisey Shell Pits Hillsborough County, Florida. (B) Specific location map ofLeisey Shell Pit 1 and 3. 168 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, PT. L No. 6 COMPOSITE SECTION COMPOSITE SECTION LEISEY SHELL PIT I LEISEY SHELL PrT 3 HILLSBOROUGH CO., FLORIDA HILLSBOROUGH CO., FLORIDA depth bilow ground Ourla- (m) -0 OA 4 modern soll zone 0.4 m, modem goll zone (removid) - - 11 m, unconsolidated uncon51*ted 68 ~ 1O H -ld 3N 3001513ld guam cand - quart: -nd 6 E 6=UPPER SHELL BED ~ ~ » 1.5 m. bull locream, 4 Esandy, massive shell t 2 - bed . .0 4 •16 •an~L BONGED- UPPER SHELL BED ~2 3.0 m, bull, sandy, ~ LOWER SHELL BED massive shell bed O 5- 1H pun uot,euuod w ouues - 3.3 4 cream to blulsh, - - - . W - sandy, massive shell bed 0.4 m. Iholly,dolorrL, -hard layer Z 0.1 y~ shel~y, mu€ly, BO~E BED- ~ B - * 1.0 m,dark, sandy mud; 5 5 freshwater shells; bones LOWER SHELL BED i - 4.3 m, blulsh, sandy, massive shell bed 10 * position of freshwater blvalves (*~2rk, sandy 2\ mud _ I modern mean Bea level tan, hard, massive, ~ ~ phosphatic dolomite 0 a 0 1 Figure 2. Composite geologic sections of L~isey Shell Pit 1 and 3 modified slightly from Hulbert and Morgan (1989). The position fromwhich the freshwaterbivalves were collected isalsoshown provided notes on the stratigraphy of the south Florida marine deposits. Steven Stanley, Johns Hopkins BOGAN & PORTELL: FRESHWATER BIVALVES FROM LEISEY SHELL PIT 169 University, Baltimore, Maryland, is thanked for discussing the complexities of the Plio-Pleistocene stratigraphy and the problems ofdating these deposits. Thomas M. Cronin. U.S. Geological Survey Reston Virginia, discussed the problems of sea level fluctuations and the difficulties in dating various outcrops. Warren Allmon. Paleontological Research Institute, Ithaca. New York. also discussed his views of the dating ofthe Ple~,-ne fossiliferous deposits ofsouth Florida. George M Davis and Gary Rosenberg Department of Malacology, Academy of Natural Sciences of Philadelphia, are thanked for providing access to the Academy collections. We acknowledge the support of National Science Foundation Grant BSR9002689. An earlier vmion ofthis paper was presented at the American Malacological Union Annual Meeting, Woods Hole, Massachusetts, June 1990 (Bogan and Portell 1990). This is University of Florida Contribution to Paleobiology number 388. MATERIALS AND METHODS The 37 unionid valves discussed here were collected between 1984 and 1990 (Table 1). Frank Garcia collected the pair ofMegalonaias boykiniana valves (Figure 3) from spoil and Gary Morgan collected the five valves of EUiptoideus sloatianus and one valve of Megalonaias boykiniana from in situ freshwater lenses at the base of Leisey Shell Pit 1. Roger Portell and Kevin Schindler collected a total of 30 valves of Utterbackia sp. cf. U. imbecillis, cf. Utterbackia sp., Megatonaias boykiniana, and Fillosa sp. from the base of the lowermost shell bed at Leisey Shell Pit 3. All specimens were stabilized using Butvar 76 thinned with acetone and the fragile valves of Utterbackia were left on matrix. Individual valves were compared to Recent specimens housed in the Malacology Collection and the Pliocene fossil material in the Invertebrate Paleontology Collections of the Florida Museum of Natural History and the Academy of Natural Sciences of Philadelphia. The taxonomy utilized in this report follows that of Turgeon et al. (1988). A list of all unionid specimens with identification, description of valve, and from which Leisey Shell Pit the material was collected is presented in Table 1. Summary offreshwater bivalves from the Leisey Shell Pits. Number of valves signified with a 'V. Tan Leisey Pit 1 Leisey Pit 3 Utterbackia 4 U. imbecillis 15v d. Unerbackia sp. - 1 v Eliiptoideu, sloatianus 5v Megalonaias boykiniana 3v 10 v MUosa sp - 1v Indeterminate Unionidae 2v Total 10 v 27 v 170 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL. 37, PT. I, No. 6 I 4 C Figure 3. Megalonaiai boykiniana (Lea), UF 9213. (A) external view of left valve, (B) internal view of left valve. Valve length is 11.7 cm and height is 10.5 cm. BOGAN & PORTELL: FRESHWATER BIVALVES FROM LEISEY SHELL PIT 171 Appendix 1. All of the specimens discussed in this paper are reposited in the Invertebrate Paleontology Division at the Florida Museum of Natural HiStOfy, Gainesville, Florida AGE OF FAUNA The in sin, freshwater bivalves from the base of the lowermost shell bed at Leisey Shell Pit 1 are from below the lowest strontium sample with a reported date of 2.4 myr and the Utterbackia are from below the lowest strontium sample taken at Leisey Shell Pit 3 with a reported date of 2.07 myr (Jones et al., this volume). The date of 2.4 myr is too old if these deposits are actually Pleistocene in age. The strontium date of 2.07 myr with an associated minimum error of* 0.57 myr results in a minimum age of 1.5 myr. The paleomagnetic samples from the Leisey Shell Pits are interpreted as being reversed and are not from the Olduvai subchron but probably represent the Matuyama Magnetochron with a date less than 1.6 myr (MacFadden, this volume). The suggested age of the vertebrate assemblage is ca 1.5 - 1.0 myr (Morgan and Hulberi this volume). Based on the date for the beginning of the Pleistocene of 1.6 myr (Berggren et at. 1985), the range of error for the strontium dates, and the paleomagnetic data, the age of the unionid samples is probably early Pleistocene, with an age of 1.6 - 1.0 myr. For a detailed discussion of the stratigraphy of the Leisey Shell Pits, see the companion papers in this volume by Morgan and Hulbert, Portell et al., Jones et al., and MacFadden. DISCUSSION The modern unionid fauna of the panhandle and peninsular Florida has been surveyed, and problems with the identification of individual species examined (Athearn 1964; Butler 1989; Clench and Turner 1956; Heard 1977, 1979; Johnson 1965, 1967, 1968, 1969, 1972, 1977; Sepkoski and Rex 1974; and van der Schalie 19404b). These reports document a decrease in the diversity of unionid species from the major river systems of the Florida Panhandle to the east and south into peninsular Florida: Apalachicola River (33 species); Ochlockonee River (20 species); Suwannee River (13 species); Waccasassa River (2 species); Withlacoochee River (9 species); Hillsborough River (9 species); Peace River (8 species); and Alafia River (6 species). This pattern of decreasing diversity in the unionid bivalve fauna from west to east along the Gulf Coast of Florida is also apparent in the freshwater fish fauna (Gilbert 1987; Swift et al. 1986: fig. 7.4). The distributional analysis of the fish fauna fits very closely with that of the unionids as presented by Sepkoski and Rex (1974). This similarity may be 172 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, Fr. I, No. 6 explained by the host/parasite relationship of freshwater fish and the unionid larval stage. The unionid genera, Utterbackia and Villosa are currently found in lakes on the Gulf Coast of Florida and in backwater areas of coastal plain rivers, typically in sand bottoms with little or no current (Johnson 1972). EUiptoideus and Megalonaias are much larger species and appear to be restricted to large rivers and streams. EUiptoideus sloatianus is presently confined to the Ochlockonee and Apalachicola River systems of Florida (Clench and Turner 1956:174-175). The fossil occurrence of these two large river species about 320 kilometers south of their known modern range is significant and documents a much wider former range. Their presence in the Tampa Bay area can only be explained by a much larger river draining this area during the early Pleistocene when sea level would have been lower than today. Based on the stratigraphic position of the unionid- bearing sediments (see Fig. 2), the sea level must have been a minimum of six to ten meters lower than present which could have allowed a river system to extend significantly farther to the west. The flat Coastal Plain would have presented opportunities for the transfer of species during nood conditions and by the confluence of many of the coastal rivers creating large complex drainages. One possible explanation for the disappearance of these species from peninsular Florida is that the present drainage basin in the Tampa Bay area is not of adequate size to supp6rt a large river and hence the species or its host fishes. The unionid fauna of peninsular Florida has decreased in diversity due to rising sea levels which caused the drowning of the lower reaches of the western rivers and severe restrictions of drainage basins. LITERATURE CITED Athearn, H.D. 1964. Three new unionids from Alabama and Florida and a note on Lampsilis jonesi. Nautilus 77(4):134-139, pl. 9 Berggren, W. A, D. V. Kent, J. J. Fl>,in, and J. A Van Couvering 1985. Cenozoic geochronology. Geol Soc. Amer. Bull. 96:1407-1418. Bogan, A E., and F. V. Grady. 1991. Two Pleistocene molluscan faunas from eastern West Virginia. Pp. 189-213 in J. R. Purdue, W. E. Klippel and B. W. Styles, eds. Beamed bobwhites and blue-points: Tributes to the career of Paul W. Parmalee. Illinois State Mus. Scien. Pap. 23, and Univ. Tennessee Dept. Anthro. RepL Invest 52. Bogan. A E., E. E. Spamer, G. C. Manville, W. B. Gallagher and A. J. Cain. 1989. Preliminary reexamination of the Fish House Local Fauna and Flora (Pleistocene), Pennsauken, Camden County, New Jersey. Mosasaur 4:111-126. Bogan, A E., and k W. Portell. 1990. Early Meistocene Unionidae from southern Florida (Bivalvia). Amen Malao. Union Prog. & Abst, 56th Ann Mtg.. Woods Hole, Massachusetts, p. 29. Butler, R. S. 1989. Distributional records for freshwater musseis (Bivalvia: Unionidae) in Florida and South Alabama, with zoogeographic and taxonomic notes. Walkerana 3(10):239-261. Clench W. J., and R. D. Turner. 1956. Freshwater mollusks of Alabama, Georgia, and Florida from the Escambia to the Suwannee River. Bull. Florida State Mus., Biol. Sci. 1(3):97-239. BOGAN & PORTELL: FRESHWATER BIVALVES FROM LEISEY SHELL PIT 173 Dall, W. H. 1898. Contributions to the Tertia,y Fauna of Florida with especial reference to the Silex Beds of Tampa and the Pliocene Beds of the Caloosahatchie River. Part iv. L Prionodemnanea: Nucula to Julla. II. Teleodesmacea: Teredo to Ervilia. Trans. Wagner Free Inst Sci. Philadelphia 3(4):571- 931. Gilbert, C. R. 1987. Zoogeography ofthe freshwater fish fauna of southern Georgia and pen,n~,lar Florida. Brimleyana 13:25-54. Heard, W. H. 1977. Freshwater Mollusca of the Apalachicola Drainage. Pp. 20-21 in R. J. Livingston and E. A Joyce, Jr., eds. Proceedings of the conference on the Apalachicola Drainage System, 23-24 April 1976, Gainesville, Florida. Florida Mar. Res Publ. No. 26. Florida Dept Nat. Res., Mar. Res. Lab., St Petersburg . 1979. Idcntification manual ofthe freshwater clams of Florida. Florida Dept. Environ. Reg, Tech. Ser. *2):143,88 figs Henderson, J. 1935. Fossil non-marine Mollusca of North America. Geol. Soc. Amer. Spec. Pap. No. 3, i- vii. 1-313. Hulbert, R. C. Jr., and O. S. Morgan. 1989. Stratigraphy, paleoccology. and vertebrate fauna of the Leisey Shell Pit Local Fauna. Early Pleistocene (Irvingtonian) of southwestern Florida. Pap. Florida Paleon. 2,1-19. Johnson, k I. 1965. A hitherto overlooked Anodonta (Mollusca: Unionidae) from the Gulf Drainage of Florida Breviora 213:1-7, pt. 1-2. 1967. Additions to the unionid fauna of the Gulf Drainage of Alabama, Georgia and Florida (Mollusca. Bivalvia). Breviora 270:1-21, pl. 1-3. 1968. EU,ptio nigella, overlooked unionid from Apalachieola River System Nautilus 82(1):22- 25,6 figs 1969. Further additions to the unionid fauna ofthe Gulfdrainage of Alabama, Georgia and Florida Nautilus 83(1):34-35. 1972. The Unionidae (Mollusca: Bivalvia) of peninsular Florida. Bull. Florida State Mus., Biol. Sci. 16(4):181-249. . 1977. Monograph of the genus Medionidus (Bivalvia: Unionidae) mostly from the Apalachicolan Region, Southeastern United States. Occ. Pap. Mollusks *56):161-187, pls. 17-19. Kat, P. W. 1983. Fossil evidence from Fish House clays for the origin and changes in species composition through time ofthe northern Atlantic Slope unio:lid fauna (Mollusca: Bivalvia). Proc. Acad. Nat Sci. Philadelphia 135:85-101. L.amarck, J. B. 1819. Lcs Nayade* Pp. 67-89 in Histoire Naturelle des Animaux San Vertebres Vol. VI. LEK 1. 1840. Descriptions of new fresh water and land shells. Proc. Amer. Phil. Soc., Philadelphia 1. 284-289. MacNeil. F. S. 1935. Freshwater mollusks from the Catahoula Sandstone (Miocene) of Texas. J. Paleon. 9:(1):10-17. Marshall, W. B. 1929. New fossil land and fresh-water mollusks from the Reynosa Formation of Texas. Proc. U. S. Nall. Mus. 76(2798)14, pl. 1. Modell, H. 1957. Die fossilen Najaden Nordamerikas. Ein Klassifizierungsversuch. Archiv fOr Molluskenkunde 86(4/6): 183-200. Pilsbry, H. A 1953. Fresh-water mollusks. Part III-B. Pp. 439447 in AA Oisson and A Harbison, eds. Pliocene Mollusca of Southern Florida with special reference to those from North Saint Petersburg Monogr. Acad. Nat. Sci. Philadelphia No. 8. Say, T. 1829. Descriptions of some new terrestrial and fluviatile shells of North America. New Harmony Dissaninator 1829:354-335. Sepkoski, J. J., Jr., and M. A Rex 1974. Distribution of freshwater mussels: Coastal rivers as biogeographic islands, Syi Zool. 23(2):165-188 Swift, C. C., C. R Gilbell, S. A Bottone, G. H. Burgess, and R. W. Yerger. 1986. Zoogeography ofthe freshwater fishes of the southeastern United States: Savannah River to Lake Pontchartrain. Pp. 213- 265 in C H Hocutt and E. 0. Wiley, eds. Zoogeography ofNorth American freshwater fishes. John Wiley and Sons, New York. Turgeon, D. D., A E. Bogan, E. V. Coan, W. K Emerson, W. G. Lyons, W. L Pratt, C. F. E. Roper, A Scheltema, F. G. Thompson, and J. D. Williams. 1988. Common and scientific names of aquatic invertebrates from the United States and Canada: Mollusks. Amer. Fish. Soc. Spec. Publ. 16:vii, 1- 277, 12 color plates. 174 BULLETIN FLORIDA MUSEUM NATURAL. HISTORY VOL 37, M. I, No. 6 van der Schalie. H. 19404 Lampsill,jonesi, a new naiad from southeastern Alabama. Nautilus 47(4)125- 127. . 194Ob. The naiad fauna ofthe Chipola River, in no:thwestern Florida. Uoydia 3:191-208, pls. 1-3. BOGAN & PORTELL: FRESHWATER BIVALVES FROM LEISEY SHELL PIT 175 APPENDIX 1 The following is a list of all unionid specimens with identification description of valve and from which Lcisey Shell Pit the material was collected. Utterbackia sp. d U. imbeciths (Say 1829). All specimens have a straight hinge line with the beak belowthe level of the hinge. Leisey Shell Pit 3: UF 31472. 1 right valve fragment of hinge line and disc very distinct, wavy beak sculpture. UF 31473. 1 leR valve fragment with hinge line. enough of the disc remains to show inflation of the shell, very distinct wavy beak sculpture, on matrix UF 31474. 1 right valve fragment with hinge line. good wavy beak sculpture, on matrix. UF 31475. 1 right valve fragment with hinge line and disc, faint evidence of wavy beak sculpture, on matrix. UF 31489. 1 leR valve fragment with hinge line, good wavy beak sculpture, on matrix UF 31491. 1 right valve hinge fragment. thin shell, with distinct beak sculpture of v and straight line sculpt,re. UF 31492. 1 leR valve fragment with hinge line and disc, no beak sculpture observed, also what appears to be periostracum retained, on matrix UF 31493. 1 left valve Ragment of hinge line with clear concentric beak sculpture. UF 31494. 1 left valve fragment of hinge line with wavy beak sculpture. UF 31495. 2 fragments of same right valve central disc area, no hinge line. UF 314%. 1 fragment ofright valve disc area, no hinge area or beak, somewhat inflated shell. UF 31498. 1 fragment ofteft valve disc area. no hinge area or beak inflated shell. UF 31499. 1 left valve fragment with hinge line and beak, beak at hing¢ line, wavy beak sculpture. UF 39661. 1 left valve, nearly complete, lacking posterior and ventral margins. cf. Utterbackia sp Leisey Shell Pit 3: UF 31490. 1 valve fragment, resembles other Unerbackia specimens, on matrix Elliptoideus sloatianus (bea \840') Leisey Shell Pit 1: UF 3%71. 2 right valves with hinge line and disk area of shell, lacking posterior and ventral margins. UF 39670. 1 left and 1 right valve with hinge line and disk area of shell, lacking posterior and ventral margins. UF 39669. 1 right valve with hinge line and disk area of shell, lacking posterior and ventral margins. Megalonaias boykiniana (Lea 1%40) Lelsey Shell Pit 1: UF 39668. 1 left valve with external sculpture and deep beak cavity. missing posterior and ventral margins. UF 9213. 1 right and 1 left valve, a pair, complete except for the posterior margin, external surface of shell with sculpture intact Leisey Shell Pit 3: UF 31476. i left valve fragment with outside intact missmg dorsal and posterior edges, lateral teeth and interdentum missin& UF 31477. 1 right valve fragment with outside intact. missing dorsal and posterior margins, lateral teeth and interdentum missing UF 31478. 1 right valve fragment with umbo area and pseudocardinal teeth present and part of the disc of the shell, some exterior surface ofthe shell remains. interdentum and lateral teeth missing UF 31479. 1 left valve fragment with un*o and part ofthe disc prescrved, lacking the interdentum and lateral teeth, some external mirface remains, UF 314SO. 1 valve fragment with umbo and disc to ventral margin, lacking lateral teeth, with some external surface intact. 176 BULLETIN FLORIDA MUSEUM NATURAL HISTORY VOL 37, Fr. I, No. 6 UF 31481. 1 left valve fragment with umbo and disc, lacking interdentum and lateral teeth. no external surface remaining UF 31482. 1 right valve umbonal fragment with pseudocardinal teeth and beak cavity but lacking the lateral teeth. no external surface remains UF 31483. 1 right valve umbo and disc fragment lacking interdentum and lateral teeth, no external surface remains. UF 31484. 1 right valve umbo fragment lacking interdentum and lateral teeth, no external surface remains UF 31485. 1 left valve umbonal and disc fragment with pseudocardinal teeth and posterior section oflhe valve, lacking lateral teeth. UF 31486. 11 shell fragments associated with the valves of Megalonaias - 3 fragments are from valves just ventral and posterior to the umbo, 2 have pedal retractor muscle scars. Maosa sp I,eisey SheII Pit 3: UF 31488. 1 right valve with umbo area with broken pseudocardinal and lateral teeth and some of the disc ren~ning, Indeterminate Unionidac Lebey Shea Pit 1: UF 39667. 1 left valve with anterior portion of lateral teeth, broken pseudocardinal teeth, missing anterior, posterior and ventral margins, no external surface rernainA. Based on the hinge area and the thickness ofthe shell. this fragment resembles Elliptio crassidens (Lamarck 1819). I,eisey Shell Pit 3: UF 31497. 1 right valve missing anterior, posterior and ventral margins, hinge line present but eroded valve thickened anteriorly and thinning posteriorly. This valve resembles specimens of Obovana but is too fragmentary for identification.