UPPER TENNESSEE DRAINAGE. 549 
while the form coccineum is scarce, and the typical obliquum is 
absent. 
Type locality: Scioto River, Ohio. 
28. PLEUROBEMA OBLIQUUM COCCINEUM (Conrad), 1836. 
Unio coccineus Conrad, ’36.—Pleurobema coccineum Ortmann, ‘120, 
p. 263 (anatomy).—Pleurobema sp. ? Goodrich, ’13, p. 94.— 
Quadrula coccinea Simpson, ’14, p. 883. 
A compressed form, typically merely a compressed catillus, 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 coccineum 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 catillus 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. 
