CONCHOLOGIA CESTRICA. 8/ 



Shell, heavy, ovate, or rhomboid, inequilateral, round 

 before, sub-angulaf 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. i-i j, inches. 

 Very variable. 



Station, ponds and running streams. Chester County; 

 everywhere common. 



U. radiatus, LAMARCK, An. Sans. Ver., VI., 1819. 



U. radiatus. 



Fig, 182. 



Shell, transversely ovate, compressed; anterior end 



