Interior Low Plateau Distributional Patterns 171 



scarcely open to argument. The Coosa River had more endemic species 

 of operculated gastropods than any other river in North America 

 (Goodrich 1944a), including members of the families Pleuroceridae and 

 Viviparidae. Two of eleven species of Somatogyrus that occur in the 

 Coosa also live in the Tennessee River, and Goniobasis carinifera 

 (Lamarck) lives in both drainages (Goodrich 1944a). 



A very characteristic pleurocerid genus of the Alabama-Coosa sys- 

 tem is Anculosa (Leptoxis, according to Burch 1982), which has a large 

 number of endemic species not found outside that system but also has 

 derivatives that occur elsewhere (Goodrich 1922). Some of these species 

 occur in Low Plateau drainages, including the related genus Nitocris 

 (Branson 1972). Nitocris (relegated to Mudalia by Burch 1982) has been 

 able to extend its range into the Kanawha of West Virginia, the Hiwas- 

 see of North Carolina, the Tennessee River, and the Ohio and Little 

 Miami of Ohio, Indiana and Kentucky (Goodrich 1940, 1944a). Ala- 

 bama River derivatives of Anculosa occur in the Tennessee, Cumber- 

 land and Green rivers (Burch 1982; Goodrich 1934). Anculosa subglo- 

 bosa Say lives in the Cumberland River system of central Tennessee 

 (Goodrich 1921). Anculosa praerosa Say, a secondary Tennessee River 

 system derivation, occurs in the Tennessee system; in the Cumberland, 

 Holston, Duck, Clinch, Little Tennessee, and Obey rivers of Tennessee; 

 in tributaries of the Duck and Tennessee rivers in Alabama (Burch 

 1982; Goodrich 1944b; TV A 1975); and in the Blue and Wabash rivers 

 of Indiana. Thus, it is clear that streams of the Interior Low Plateau 

 have served as important migration pathways into the Ridge and Valley 

 Province and elsewhere. 



There are many endemic pleurocerid species in the Tennessee and 

 Cumberland river systems (Goodrich 1940). Pleurocera prasinatum 

 (Conrad) of the Alabama River system is most closely related to P. 

 canaliculatum (Say) (Goodrich 1935), various forms of which occur in 

 the Tennessee, Cumberland, Clinch, Kentucky and Ohio rivers. It has 

 also been able to penetrate into the Wabash of Indiana (Goodrich 

 1929), doubtless via the Ohio since the ancestral Wabash of Indiana and 

 Illinois was almost completely overwhelmed during Wisconsin glacia- 

 tion. Lithasia obovata (Say) and L. geniculata Haldeman are both con- 

 sidered Tennessee River derivatives. Lithasia geniculata is relatively 

 widespread in the Interior Low Plateau of the Tennessee River in Ten- 

 nessee (Burch 1982). It was recently discovered in the southwestern sec- 

 tion of the Kentucky portion of the Low Plateau (Branson et al. 1983), 

 and is common in parts of the lower Tennesse (TV A 1975). Lithasia 

 obovata had spread from the Tennessee River basin into the Green, 

 Cumberland and Kentucky river basins and, via the Ohio River, into 

 the Wabash of Indiana and the Scioto of Ohio (Goodrich 1929). 



