800. PLEUROBEMA 
This may be a distinct species, but I do not feel like separat- 
ing it on the limited amount of material I have seen. The 
surface is quite dull and rude; the anterior basal part of the 
nacre is quite solid, becoming suddenly thinner at the cavity 
of the shell. 
PLEUROBEMA CONASAUGENSE (Lea). 
Shell long rhomboid, solid, subinflated, inequilateral ; beaks 
moderately full and high; posterior ridge well developed, 
somewhat double, ending behind in a biangulation near the 
base of the shell; anterior end rounded; base line nearly 
straight ; posterior end obliquely truncated above; the trunca- 
tion joining the slightly curved dorsal line at an angle; sur- 
face with irregular growth lines; epidermis dark tawny or 
brownish, concentrically wrinkled, almost cloth-like; left valve 
with two triangular pseudocardinals and two short, curved 
laterals; right valve with one pseudocardinal and two rudi- 
mentary ones, with a double lateral; beak cavities not deep; 
muscle scars well impressed; nacre soiled whitish. 
Length 65, height 40, diam. 26 mm. 
Upper Tennessee River drainage. ' 
Type locality, Conasauga Creek, Monroe Co., Tenn. 
Unio conasaugaensis Lea, Pr. Ac. N. Sci. Phila., II, 1872, p. 
r553 Jin Ace, No se Phila Vu e743, pLisees 40. 
Obs), XT 18745 p27,eple ype 30: 
Pleurobema conasaugaensis SIMPSON, Syn., 1900, p. 763. 
A subinflated, rather solid species, which is close to P. breve. 
It is a little more inflated, heavier and more elongated than 
that species. The form from Hardy, Arkansas, which I called 
variety subelliptica of breve might as well be considered a 
variety of conasaugense as specimens seem to almost connect 
the two. 
PLEURORRMA BREVE (Lea). 
Shell rhomboid or somewhat subtriangular, compressed or 
subcompressed, rather solid, somewhat inequilateral; beaks 
apparently only moderately full or high; posterior ridge strong, 
narrowly and feebly double, ending in a biangulation at the 
