95 



UNIO CERINUS. 



Plate LII. 

 DESCRIPTION. 



Shell triangular, subrhomboidal, compressed; disks 

 flattened, slightly undulate; ligament margin slightly 

 declining; posterior margin obliquely truncated, ex- 

 tremity obtusely angulated; umbonial slope angulated; 

 beaks decorticated, not prominent; anterior margin 

 truncated above; basal margin widely and slightly 

 emarginate; epidermis brownish-yellow; within white 

 with wax-yellow stains; cardinal teeth direct, robust, 

 single in one valve and double in the other; lateral 

 teeth rectilinear. 



OBSERVATIONS. 



A few specimens of this species were sent me from 

 New Orleans by Mr. Josiah Hale. It probably in- 

 habits the waters of Louisiana, not far from New 

 Orleans. The two most characteristic species of 

 Louisiana were contained in the box of specimens, U. 

 Mortoni and U. Hydianus, Lea, and also U. Hcmbeli. 



It has a general resemblance to U.flavus and sub- 

 planus; from the former of which it may be distin- 

 guished by its much less prominent beaks, more 

 compressed disks and proportionally longer outline: 

 it differs from the latter in having a broader umbo, 

 emarginate base, longer ligament margin, less oblique 

 posterior margin, truncated anterior margin, and 

 more robust cardinal teeth. Old shells have some- 



N 



