Mr. Barnes on the Genera Unio and Alasmodonta. 269 
nent, the rays fewer, Mite the — less brilliant. It ap- 
proaches the Unio Cariosu 
—Inhahits the Delaware at New Hope: Mr. ie: Sears. 
My Collection. 
Remarks.—With the most decal deference to the 
two distinguished Naturalists whose names are mentioned 
above, I have ventured to differ from them both, as they do 
from each other. I think a slight examination of our Cab- 
inets would convince either of them that this shell requires 
a separate designation. Two bivalves can scarcely be 
more unlike than this and the Unio Radiata of Lamarck; and 
the recent discovery, of the variety C, in our own waters, 
which produce thousands of the Unio Cariosus, seems con- 
clusive as to that. . This variety it will be observed has 
precisely the same diametes and length as the shell from the 
W ioc pean and the difference in the teeth may be acciden- 
is the same necessity for distinguishing these 
as any etlisie. They are totally unlike. 
| outline 
21. Unio Siniquorwevs. Fig. 15.< of the 
| shell. 
Shell long-ovate, sub-cylindrical, thick, regularly 
rounded, rayed, beaks slightly elevated, cavity 
small ; inside white 
Inhabits the Ay aisbitet Douglas 
Dr. Mitchill’s Cabinet. My Colle ction 
Diam. 1°3—1°6 Length 1-8—2-1 ae dth 3:3—3°8, 
Shell elongated pineoe disks swelled ; beaks about 
one roar) from t he gen a a hin e margin 
and lamellar on the anterior slope; smooth and bright on 
je nay of the disks; cardinal ee elevated crest-like 
ressed, and very oblique; i in some specimens nearly 
parallel to the edge of the shell; hieg teeth long and 
