88 CONCHOLOGIA CESTRICA- 
narrow, rounded; posterior, broad and rounded; dorsal 
margin elevated behind the hinge; inferior curved; 
beaks moderate; epidermis mostly greenish - yellow, 
with numerous broad, dark-green rays; interior yellow- 
ish, and iridescent; cardinal teeth bifid, crenulated, and 
oblique. H. 2-2%, W. 3-4, T. 1-1¥%, inches. 
Station, Schuylkill River, Chester County. 
U. caniosus, Say, ‘Nich, Encye;, ast) Amer Ede 
1816. 
U. cariosus. 

Shell, valves rather thin, sub-oval, inflated; hinge 
margin elevated, base curved; anterior end_ short, 
rounded, posterior narrowly rounded; the posterior 
dorsal slope sometimes with four, or five, fine inter- 
rupted wrinkles, and green rays; beaks at one-fourth 
from the anterior end; yellow or greenish; inside 
bluish-white ; cardinal teeth long, compressed, oblique, 
crenate. H. 2:5; Weeg5: 151-75, inches: 
Station, Schuylkill, Delaware, and Susquehanna Riv- 
ers; common. 
