Mollusca From Little South Fork Cumberland River 107 



in fact a confusion with specimens of T. lividus. Morrison (1969) listed 

 Toxolasma Raf. 1831 as an earlier available name for Carunculina 

 Simpson in Baker, 1898. Johnson (1978) moved taxa from Epioblasma 

 (= Dysnomia), formerly placed in Truncilla, to the genus Plagiola, and 

 recognized the lectotype of Plagiola interrupta Raf., 1820 (Johnson and 

 Baker 1973). If the Poulson Collection of Rafinesque's types (see Vanatta 

 1916; Walker 1916) is accepted, then Johnson's revision based on the 

 type of Plagiola interrupta (= Dysnomia brevidens [Lea, 1934]) is accu- 

 rate. Our examination of the lectotype of P. interrupta confirms that it 

 is a female Epioblasma brevidens. 



Rafinesque's types also affect two other taxa. Lampsilis ovata card- 

 ium Raf., 1820 (= L. o. ventricosa Barnes, 1823) is based on Raf- 

 inesque's type from the Poulson Collection (Johnson and Baker 1973; 

 Walker 1916; Vanatta 1916). The use of Potamilus (- Proptera) may be 

 argued on the basis of priority, i.e., Potamilus Raf., 1818 versus Pro- 

 ptera Raf., 1819. 



RESULTS 



In the combined 1977-1981 surveys, 24 species of Unionidae and 

 one species of Corbiculidae were collected (Table 3). This table repre- 

 sents the compilation of distribution data from our surveys, the KNPC 

 collections, and unpublished data from Schuster. Observed live speci- 

 mens of each species are indicated by an asterisk. There is a relatively 

 high correlation between species occurring historically in Big South 

 Fork and species currently occurring in Little South Fork. However, 15 

 species are conspicuously absent (Table 2). Some species, such as Ellip- 

 tic) crassidens, may have been excluded by preferences for a larger river 

 habitat. However, the majority of species, such as Fusconaia barnesiana 

 and Hemistena lata, are normally associated with other rivers the size of 

 Little South Fork. Comparable rivers, such as the Stones (Wilson and 

 Clark 1914), upper Powell (Ahlstedt and Brown 1980), middle Duck 

 (Ahlstedt 1981), upper Holston (Stansbery 1972; Stansbery and Clench 

 1974, 1975, 1978), and the Rockcastle (Williamson 1905) all contain 

 taxa absent from Little South Fork. It seems probable that the require- 

 ments of the 15 absent species are similar to those of the documented 

 species in Big South Fork and Little South Fork. 



Table 3 is a compilation of molluscan collections at respective sta- 

 tions on Little South Fork. There is a pattern of longitudinal diversity, 

 with species being added as one moves downstream from Station 2. 



From January 1980 to October 1981 there was a 37 cm shortage 

 from mean average rainfall. Due to this prolonged dryness, during our 

 quantitative sampling the entire river downstream from Station 13 

 (approximately 3 km above Ritner Ford) entered a sandy pool and fil- 



