38 



wide and prominent; beaks slightly elevated; epider- 

 mis brown olive, with angular spots disposed in form 

 of rays; cardinal teeth direct; subpyramidal, promi- 

 nent; within white; cavity capacious. 



OBSERVATIONS. 



This shell is distantly related to U. ovatus, Say. 

 but is more elongated, less ventricose, and has inter- 

 rupted rays; the epidermis posteriorly has numerous 

 short vermicular raised lines. I found the species 

 only on the bank of Elk river, near its junction with 

 the Tennessee at the Muscle shoals. 



UNIORUBELLUS. 

 Plate W.~Fig. 2, 



DESCRIPTION. 



Shell suborbicular, ventricose, thick; beaks sub- 

 t-entral; umbones prominent; umbonial slope rounded, 

 margined before by a faint angle; a similar angle be- 

 hind the umbonial slope; beaks eroded, slightly pro- 

 minent; epidermis reddish brown; cardinal teeth di- 

 rect; muscular impressions small and distinct; nacre 

 pink or purplish. 



OBSERVATIONS. 



A small species, which I obtained only in the Black 

 Warrior, near its source, among the mountains of 

 Alabama; it is rather an obscure species, but I can- 



