UPPER TENNESSEE DRAINAGE. 549 



while the form coccineiim is scarce, and the typical obliqmun is 

 absent. 



Type locality: Scioto River, Ohio. 



28. Pleurobema obliquum coccineum (Conrad), 1836. 



Unio coccinens Conrad, '36. — Pleurobema coccineum Ortmann, '12&, 

 p. 263 (anatomy). — Pleurobema sp. ? Goodrich, '13, p. 94. — 

 Quadrula coccinea Simpson, '14, p. 883. 



A compressed form, typically merely a compressed catilhis, with 

 the radial furrow absent. 



Such forms have been reported hitherto only once from the upper 

 Tennessee by Call (from " Holston River"). I have found only a 

 few of them, corresponding entirely to the cocciiiettm of the upper 

 Ohio drainage in Pennsylvania; in the Clinch at Solway, Knox Co., 

 Tenn., and in the Holston at Hodges, Jefferson Co., and at Noeton, 

 Grainger Co., Tenn. They stand very close to the catilhis forms of 

 this region, representing merely an individual variation of it. 



Type locality: Mahoning River, near Pittsburgh (= Mahoning 

 River, Lawrence Co., Pa.). 



In addition to the above form, there is, in the upper Clinch, a 

 very peculiar form of this group, not found elsewhere, which may 

 be described as a compressed obliquum, with traces of the radial 

 furrow still present. I have seen the soft parts of this (including 

 a gravid female), so that there is no doubt about the affinities of this 

 shell. This form requires further study, and might deserve a varietal 

 name, for it is found, in the Clinch, at, and a good deal above, the 

 upper limit of P. obliquum. 



In the Walker collection there are several such specimens from 

 Needham's Ford, Union Co., Tenn., and I have it from Clinchport, 

 Scott Co., Va., and from Cleveland, Russell Co., Va. 



This form may be more abundant in the poorly known portion 

 of the Clinch from Claiborne and Grainger Cos., through Hancock 

 Co., Tenn., to the Virginia state line. 



