29 
UNIO Solan dri. 
TAB. DXVIL 
Spec. Char. Transversely oblong-ovate,, slightly 
arched, rather compressed, thin ; both extre- 
mities obtuse ; beaks small, rugose ; hinge 
slender. 
Syn. Mya Pictorum. Brander , 95 ? 
Exactly twice as wide as long ; the posterior extre- 
mity is rather square and more compressed than the 
other ; the superior and inferior edges are parallel and 
a little arched ; the beaks are slightly waved or rugose. 
This beautifully pearly shell resembles the Unio ba- 
tava of Lamarck, but is more compressed : it differs 
from U. Pictorum of the same author in the square form 
of the posterior extremity, and from both in being a 
little curved. It appears from the cast that the mus- 
cular impressions are not deep, and there is only a small 
space left for the hinge, the teeth of which we have not 
been able to extricate ; the general contour of the shell, 
its rugose umbones, and brilliant pearl are so charac- 
teristic of the genus Unio, that even if the hinge were 
