74 Kenneth T. Wilkins 



other Thomomys material reported from the southeastern United States 

 is from Sabertooth Cave (Rancholabrean, Citrus Co., Florida). Simp- 

 son's (1928) description of the species referred only to skull material, 

 none of which is available in the Rock Springs deposit. Pending further 

 study, the Rock Springs Thomomys is tentatively referred to orientalis. 



The Rock Springs site has yielded additional geomyid material for 

 which generic assignment cannot be made on qualitative grounds. Sim- 

 ilarity in size and preservation to the Thomomys material Hsted above 

 suggests that four mandibles lacking cheekteeth (UF 46577-46580) are 

 referable to Thomomys. No effort has been made to identify isolated 

 lower P4's (UF 46581) and molars (UF 46582) beyond the family level. 



Family Castoridae 

 Castor canadensis ¥.\x\i\ \%20 



Material. — Lower molar (V-4399). 



Remarks. — The presence of beaver in the Rock Springs fauna was 

 previously noted by Johns (1958), who argued that its present distribu- 

 tion (restricted in Florida to the panhandle and northern peninsula) is 

 less extensive than it was in historic and Pleistocene times. The Rock 

 Springs specimen, coupled with two nearly complete mandibles with P4- 

 M3 (V-5403) from the shores of nearby Lake Monroe, Volusia County, 

 comprises the species' southernmost Pleistocene record in Florida. Post- 

 Wisconsinan records include specimens from middens in Seminole, 

 Volusia and Brevard counties (Furgeson 1951) and along the Indian 

 River (Allen 1942). 



Family Cricetidae 

 cf. 5/gmo<io« Say and Ord 1825 



Material. — Two isolated upper incisors (UF 48999). 



Remarks. — Comparison of these incisors with modern Sigmodon 

 hispidus and other rodents from Florida suggests this generic assign- 

 ment. Martin (1974) recognized the occurrence of two species of cotton 

 rats, S. bakeri and S. hispidus, in the United States and Mexico during 

 the late Irvingtonian and Rancholabrean. Identification to species 

 requires molar teeth. 



