UNIO 627 
terior ridge, which is well rounded, and sometimes has faint, 
curved, raised, radial lines in the anterior part of the shell. 
which are shown in the figure of Fischer and Crosse though 
they do not call attention to the fact. They state that the 
pseudocardinals of the right vaive are equal in size, which is 
the case in some specimens but not in all. The shell is often 
longer in proportion than theirs. 
Group of Umio buckley. 
Shell oval, obovate, subtrapezoidal, or elliptical, with a more 
or less developed posterior ridge, often biangulate behind, 
compressed or inflated, thin or somewhat solid ; beaks generally 
full, sculptured with several rather strong concentric ridges, 
which are either nearly parallel with the growth lines or slight- 
ly doubly looped; posterior slope often faintly wrinkled; epi- 
dermis usually smooth and shining in the younger shells, often 
rough when old, becoming darker with age, rayed when young. 
Hinge teeth solid or compressed; nacre mostly brilliant, of 
many shades. Animal not differing especially from that of 
closely related groups. 
UNIO BUCKLEYI Lea. 
Shell generally long ovate, rarely subrhomboid or somewhat 
obovate, subinflated to inflated, subsolid to solid, inequilateral ; 
beaks rather full and high, their sculpture consisting of nu- 
merous, slightly doubly-looped ridges; dorsal slope sometimes 
carried up, especially in the younger shell, so as to form a 
small wing, in which case the general outline is somewhat 
rhomboid; posterior ridge usually full and rounded, ending 
behind in a blunt point at or below the median line; surface 
varying from smooth to somewhat rough; epidermis generally 
smooth and shining in the younger shells, often black and 
coarse in old ones, tawny, brownish, coppery, greenish-yellow 
or olive-green, often beautifully rayed when young; left valve 
with two usually subcompressed, ragged pseudocardinals and 
two laterals; right valve with two pseudocardinals, the upper 
