26 
OBSERVATIONS, 
This large species is remarkable for its resem- 
blance to two very different species, U. alatus, of 
Say, and U. ater, of Lina; it has an outline not unlike 
the former, but is less winged and much more con- 
vex; itis less inflated and more elongated than the 
latter, and is more angulated and truncated on the 
posterior margin. The cardinal teeth are directed 
obliquely forwards in U. ater; in this species they 
are, on the contrary, directed obliquely backwards, 
It is not an uncommon species in the Black Warrior 
river, in North Alabama, where I procured them 
in six or eight feet water, in the centre of the stream; 
the purity of the water enabled me to detect them 
with facility, although a very small portion of the 
shell projected above the surface of the mud in which 
they were always imbedded. I obtained them by 
means of a long pointed stick, with the extremity 
inserted between the gaping valves, which the ani- 
mal immediately closed with such force, that I could 
readily draw them from their tenacious beds. 
UNIO TANIAT US. 
Pirate 1V.— Fug. 2. 
DESCRIPTION. 
Shell regularly convex and elliptical, moderately 
thick, epidermis finely wrinkled, olivaceous, with 
recular green interrupted rays; beaks slightly promi- 
nent; umbonial slope rounded; ligament slope with 2 
slightly impressed line; base arcuated; cardinal and 
lateral teeth prominent; within bluish white. 



