792 PLEUROBEMA 
The shell is lighter colored than P. lenticulare, it is wider 
and more rounded anteriorly and is much lighter colored with- 
in and without, but it is quite likely only a variety of that 
species. 
PLEUROBEMA LITUM (Lea). 
Shell subrhomboid, convex, subsolid, somewhat inequilat- 
eral; beaks only moderately developed; posterior ridge rather 
strong, narrowly rounded, ending in a blunt point near the 
base of the shell; anterior end rounded ; base curved ; posterior 
end obliquely truncated ; surface with irregular growth lines; 
epidermis straw-color to tawny, finely, concentrically wrinkled, 
shining, showing the dark rest marks; pseudocardinals two 
in the left valve and one and an anterior rudimentary one in 
the right; two laterals in the left valve and one in the right ; 
beak cavities shallow; muscle scars small, not deep; nacre 
brilliant salmon or reddish, iridescent and thinner behind. 
Length 41, height 26, diam. 15 mm. 
Cahawba and Black Warrior rivers, Alabama. 
Type locality, Cahawba River, Shelby Co., Ala. 
Unio ltus ea, Pr AGN. Sei.Phila., | 1871) p. mao. ie ne. 
N.. Sct Philas VII ae74p. 17, pi wv. ne anes Oliere alien 
10745 pi 2ic Pile Vhs AT se 
Pleurobema lita Simpson, Syn., 1900, p. 761. 
I am not positive as to where this form should be placed. 
There are only two shells in the Lea collection, the larger, of 
which I have given measurements, may be adult, the other is 
a young shell. The rich, bright epidermis with its dark rest 
marks and the brilliant nacre are good characters. 
PLEUROREMA GEORGIANUM (Lea). 
Shell subrhomboid, slightly obovate, being narrower at the 
anterior end, convex, subsolid, somewhat inequilateral; beaks 
apparently not very full or high; posterior ridge narrowly 
rounded, ending below the median line in a blunt point; an- 
terior end rounded; base line curved; posterior end obliquely 
subtruncate, joining the dorsal line with an angle; epidermis 
