99 



highly polished; cardinal teeth very prominent, ob- 

 lique; lateral teeth long and rectilinear. 



SYNONYME. 



U. angustatus, Lea. Trans. Amer. Phil. Soc, new series, 

 vol. iv. p. 114, pi. xvii. fig. 43. 



OBSERVATIONS. 



Inhabits the tide waters of South Carolina. It has, 

 perhaps, more general resemblance to U. nasutus and 

 Fisherianus than to any other species, but is too ob- 

 viously distinct to need a careful comparison with 

 either. I doubt whether it occurs in any stream 

 north of the Carolinas. 



UNIO EXCULTUS. 



Plate LI V.— Fig. 1. 



DESCRIPTION. 



Shell subrhomboidal, thin, ventricose; ligament 

 margin straight, rounded at tip, scarcely oblique; 

 beaks rather distant, slightly prominent, decorticated, 

 with traces of oblique plicae, and distant from the 

 anterior extremity; anterior margin regularly rounded; 

 posterior margin rectilinear, very oblique; extremity 

 truncated or obtusely rounded, scarcely angulated; 

 epidermis olive-brown, with dark concentric bands, 

 polished; within bluish, with wax-yellow stains, and 

 highly iridescent; cardinal teeth compressed, elon- 



