27 
OBSERVATIONS. 
This shell is related to U. fasciolar is, Raf. but is 
shorter, more elliptical and convex, and is readily 
distinguished; it cannot be confounded with U. fas- 
cial a, Raf. as that species is broad and angular be- 
hind, compressed, and irregularly rayed. 
Inhabits Flint river, Morgan county, Alabama. 
UNIO TRABALIS. 
Plate III. — - Fig. 5. 
DESCRIPTION. 
Shell narrow-elliptical, subrostrated; thick before, 
and very thin on the posterior margin, which descends 
rectilinearly and very oblique; end margin obtusely 
rounded; umbones broad and prominent; beaks 
eroded; epidermis dark olive brown, rayed; within 
white, and highly iridescent on the posterior side. 
OBSERVATIONS. 
This shell has almost the form of U. nasutus, ex- 
cept that the umbones are far more prominent, and 
the rostrum is nearly on a line with the base; the 
habit is altogether different from that shell Perhaps 
it may approximate U. subrostratus , Say, a species 
I have not seen; but it differs from the description in 
being remarkably thick on the anterior portion of the 
shell 
