66 

 UNIO SOWERBIANUS. 



Plate XXXVII. — Fig. 1. 

 DESCRIPTION. 



Shell ovate, convex, with concentric furrows; disks 

 slightly gibbose in the middle; posterior side with a 

 furrow from beak to base; a slight groove on the pos- 

 terior submargin; raised radiating lines extend from 

 the angle of the larger furrow to the posterior extre- 

 mity, which is direct and slightly retuse; basal margin 

 retuse posteriorly; epidermis glabrous, with faint fili- 

 form brown rays; within purple or rose colour; car- 

 dinal teeth very large and prominent, double in each 

 valve. 



SYNONYME. 



U. sowerbianus, Lea. Trans. Amer. Phil. Soc., new series, vol. 

 v. p. 68, pi. x. fig. 28. 



OBSERVATIONS. 



The fine specimen of this beautiful and very distinct 

 species which I have figured, was kindly loaned for 

 the purpose by Mr. Featherstonhaugh, who procured 

 it from Cumberland river, Tennessee. I found one 

 in the summer of 1833 on the bank of Elk river, 

 Alabama, and judging from Mr. Lea's figure of the 

 pilcus, I supposed it to be that species.* The speci- 

 men is in the cabinet of Mr. Poulson. 



The Sowerbianus is remarkable for its highly po- 

 lished epidermis and raised lines on the posterior side. 



* New Fresh Water Shells, p. 69, note. 



