778 PLEUROZEMA 
angular, two in the left valve and one to three in the right; 
laterals two in the left valve and a somewhat double one in the 
right; beak cavities shallow; muscle scars rather small, im- 
pressed; nacre white or reddish, thinner and iridescent behind. 
Length 50, height 40, diam. 30 mm. 
Length 509, height 39, diam. 26 mm. 
Type locality, Black Warrior River, Alabama. 
Unio furvus ConRAD, New F. W. Shells, 1834, p. 39, pl. v1, 
fig. 3—CHENUu, Bib. Conch., ist ser., III, 1845, p. 20, pl. 1, 
fig. 4. 
Pleurobema furva SIMPSON, Syn., 1900, p. 758. 
I cannot be positive that the shells, which I call Pleuwrobema 
furvum, are Conrad’s Unio furvus, but I think they are. They 
agree well in shape; some of them are quite dark and they 
have the epidermis beautifully and minutely concentrically 
wrinkled, a character he notes in his description. He gives 
no dimensions, but if the shells I have are that, his figure is 
taken from a young specimen, as it is 32 millimeters long and 
18 high. 
PLEUROBEMA AVELLANA Simpson. 
Shell small, solid, inflated, inequilateral, nearly elliptical ; 
beaks full, slightly elevated; posterior ridge well developed, 
narrowly rounded, ending below the median line; anterior end 
evenly rounded ; base line curved, a little fuller in the middle ; 
outline of dorsal slope almost evenly curved, the posterior end 
narrowly rounded ; surface lightly concentrically striate, green- 
ish-brown, slightly clouded but scarcely rayed ; pseudocardinals, 
two in the left valve and one in the right; laterals, two in the 
left valve and one in the right, which is somewhat double; 
muscle scars deep; nacre bluish, iridescent behind. 
Length 30, height 20, diam. 15 mm. 
Type locality, Cahawba River, Alabama. 
Pleurobema avellana Stmpson, Pr. Ac. N. Sci. Phila., 1900, 
D. Ol, pl 1s. (6, 7; Syn), OOO mp7 Se. 
A small, compact, solid, inflated species, which is more 
nearly elliptical than P. rubeliam and differently colored. 
