CONCHOLOGIA CESTRICA. 87 
Shell, heavy, ovate, or rhomboid, inequilateral, round 
before, sub-angular behind; base curved, hinge margin 
Unio complanatus. 
Fig. 181. 

elevated, sloped posteriorly; beaks not prominent ; 
epidermis dark olive-green; rayed when young ; nacre 
varying from white to dark purple, often iridescent ; 
cardinal teeth thick. H. 2.5, W. 4-4%, T. 1-1, inches. 
Very variable. 
Station, ponds and running streams. Chester County; 
everywhere common. 
U. radiatus, LamMARckK, An. Sans. Ver., VI., 1819. 
U. radiatus. 
Fig, 182. 

Shell, transversely ovate, compressed; anterior end 
