27 



mistaken for U. cariosus. Old shells are very thick 

 and ponderous, and Mr. Poulson has a fine specimen 

 of this description. Had the Baron de Ferussac seen 

 this, we think he would not for a moment have deemed 

 it a variety of U. subovatus. Mr. Phillips has two 

 fine specimens, male and female; the former is repre- 

 sented. 



UNIO CONGARiEUS. 



Plate XII.— Fig. 1. 



DESCRIPTION. 



Shell elliptico-rhomboidal, thin, somewhat flattened 

 at the sides; epidermis olive or reddish-brown, with 

 numerous green rays, sometimes obsolete; umbones 

 flattened, broad; summits obtusely rounded, slightly 

 prominent; umbonial slope profoundly angulated; 

 ligament slope slightly oblique; posterior slope much 

 depressed, with oblique, irregular, undulated lines; 

 within white, highly iridescent; cardinal teeth oblique; 

 lateral teeth elongated, slightly curved. 



SYNONYME. 



U. congar;eus, Lea. Trans. Amer. Philos. Soc. new series, vol. 



4. p. 72. pi. vi. fig. 4. 

 Cab. A. N. S.No. 2101. 



OBSERVATIONS. 



Inhabits the eastern waters of South Carolina. I 

 found it also at Augusta, Georgia, in great numbers. 



