270 Mr. Barnes on the Genera Unio and Alasmodonta. 
straight; cavity of the beaks small and rather shallow, na- 
ker pearly white and iridescent,surface smooth and polished. 
ariety (a) shell less, more ovate, broader before, hinge 
margin more+elevated. 
- Remarxs.~This is a beautiful and elegantly formed shell. 
It somewhat resembles a pea-pod; hence its name.» It 
agrees in color and surface with the Unio Ventricosus, but 
_ differs in being of smaller size, longer in proportion, more 
cylindrical, less inflated, beaks much less elevated, and cav- 
ity less capacious. gel } 
22. Unto Ovatus.—Shell roundish-ovate, convex, 
umbones elevated, beaks recurved, anterior 1u- 
-nule flattened ; teeth crest-like elevated. 
Unio Ovatus. Mr. Say. —— 
Unio Ovata. M. Lamarck. 
Inhabits the Ohio. Mr. Collins. 
Maumee, at Fort Wayne. Mr. Sears. 
‘Mr. Collins’ Collection. My Collection. | 
Diam. 1-6—2°0 Length 2:3—3-0 Breadth 3°3—4-0. 
American Conchology, plate 2, fig. 7. 
Shell usually broader before, and narrower behind the 
beaks; but in the figure referred to above, the contrary is 
observed ; thin when young, and not remarkably thick 
when old; disks swelled; umbones prominent; ligament 
partly concealed ; anterior lunule flattened, and fuscous, 
somewhat waved with strie and wrinkles becoming lamel- 
lar; hinge margin making an angle with the anterior and 
posterior dorsal ; epidermis yellowish, or horn color; su!- 
face glabrous, deeply wrinkled, wrinkles appearing on the 
inside ; cardinal teeth crest-like, elevated and compres- 
sed; lateral teeth elevated; in some specimens, short, 
crooked, and apparently deformed; in others, straight; 
cicatrices smooth and polished ; cavity large and rendered 
somewhat angular by the flattening of the anterior slope 5 
naker pearly, bluish white ; surface, in old specimens, P? 
pillous, in young, smooth. 
Remarxs.—The angular appearance produced by the 
flattening of the anterior slope, readily distinguishes this 
