NEW 
FRESH WATER SHELLS. 
UNIO POULSONI. 
Puate I, 
DESCRIPTION. 
SHELL ovate, somewhat inflated, subalated, con- 
nate, with a blackish epidermis, profoundly wrinkled | 
posteriorly; umbones not prominent; beaks hardly 
elevated above the dorsal line; ligament margin 
slightly arched; anterior side very short, and nar- 
rowed; posterior side somewhat produced, and trun- 
cated at the extremity; two obscure carine radiate 
from the beaks behind the umbonial slope; region of 
the umbonial slope inflated; anteriorly somewhat 
contracted and gaping at the base; cardinal teeth 
directed obliquely backwards; very thick and sul- 
cated; lateral teeth short; very distant from the car- 
dinal teeth, and granulated; within dark purple; pos- 
terior margin iridescent. 
C 
