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. congarjEus, 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. 



