93 



foundly diverging; in the right valve single, robust, 

 sulcated; lateral teeth rectilinear. 



SYNONYME. 



U. patulus, Lea. Trans. Amer. Phil. Soc, new series, vol.iii. 



p. 441, pi. xii. fig. 20. 

 Cab. A. N. S., No. 20424. 



OBSERVATIONS. 



Inhabits the rivers of Tennessee and Kentucky, 

 and appears to be comparatively rare. It may be 

 distinguished from U. clava by its less oblique and 

 more compressed form; and the beaks are less pro- 

 minent and not terminal. The beaks are acutely 

 pointed at the apex, and nearly touch each other; 

 and they are somewhat flattened on the summit and 

 have tubercular undulations. It is probable that U. 

 oviformis is but a variety of this species. 



UNIO HEMBELI. 



Plate LI. Fig. 1. 

 DESCRIPTION. 



Shell elliptical, convex, posterior extremity angular, 

 much above the line of the base; posterior slope with 

 obtuse undulations; beaks eroded, scarcely elevated 

 above the dorsal line; umbonial slope undefined; epi- 

 dermis dark brown, becoming black with age, much 

 wrinkled; within white; cardinal teeth robust, double 

 in each valve, direct, profoundly striated. 



Cab. A. N. S., No. 20422. 



