268 Mr. Barnes on the Genera Unio and Alasmodonta. 
over the ligament ; ligament large and: prominent, passing 
under the beaks ; anterior lunule depressed at the margin, 
fuscous, broad-heart-shaped, longitudinally waved; hinge 
margin depressed between the beaks; posterior slope car- 
inate ; epidermis yellowish olive, becoming chesnut brown 
on the umbones 3 rayed with green, more conspicuous in 
young specimens; in old ones the dark chesnut brown 
covers the whole and conceals the rays; surface smooth and 
shining, reflecting the face of the observer; young shells 
are splendent, having a much stronger lustre on the outside 
an on the inside; cardinal teeth broad, prominent and 
obliquely flattened ; lateral teeth broad, elevated and ter- 
minating abruptly before; cicatrices large ; cavity of the 
beaks unusually large ; naker pearly white; surface smooth, 
but not highly polished. : 
Remarxs.—There is a remarkable uniformity in the di- 
mensions of the full-grown specimens of this species. This 
shell is more capacious than any other of the genus hitherto 
described. It most resembles the unio ovatus, but its great- 
er capacity, darker color, its smooth,shining and rayed sur- 
face will distinguish it without mistake. 
Variety (a) shell broader, less ovate, nearly oval and 
nded on sid 
A fine large shell. It measures 
Diam. 2.3—2.8 Length 3.1—3.8 Breadth 4.1—5.4. 
Inhabits the Wisconsan. Mr. Schoolcraft. 
Variety (+) shell light green, rayed, compressed. 
Inhabits the Wisconsan. 
Variety (c) shell with the teeth slightly elevated ; cardi- 
nal one formed by a serrated edge of the shell, and a slight 
prgecnyt within. 
nhabits Barbadoes Neck, N. J. near New-York. 
Mr. Bradhurst’s Collection. 
Diam. 2.5 Length 3.5 Breadth 4.8. ‘ 
Variety (d) a shell from the Delaware approaches this 
species. The form and colourare similar. It is howeveT 
less, the largest measuring scarcely 2.3 inches broad ; .™a- 
king the shell not more than one fifth the size of those de- 
scribed above ; also the beaks and bosses are less prom- 
