44 
nent, not nearly terminal; posterior margin obliquely 
truncated; umbonial slope rounded; base arcuated; 
epidermis olivaceous, obscurely rayed, wrinkled on 
the margins; cardinal and lateral teeth very promi- 
nent, granulated; nacre whitish and iridescent on 
the posterior margin. 
Variety A. Epidermis reddish brown; nacre rose 
coloured. 
OBSERVATIONS. 
I found a very few specimens of this shell at Clai- 
borne, on the Alabama river; it is allied to U. multi- 
radiatus, Lea, but on comparing it with specimens 
of that species in Mr. Poulson’s cabinet, I found it 
sufficiently distinct; the nacre is denser, and thicken- 
ed on the margin; and the rays are of nearly uniform 
size, distant and obscure. The lateral teeth closely 
resemble those of U. multiradiatus. 
UNIO PRASINUS. 
Plate III. — Fig. 1. 
DESCRIPTION. 
Shell suborbicular, compressed, with distant con- 
centric impressed lines; anterior margin obtusely 
rounded; posterior margin wide, truncated, not 
oblique; basal margin straight, parallel with the liga- 
ment margin; beaks prominent; epidermis olive yel- 
