59 



side produced, pointed; hinge margin elevated; pos- 

 terior margin very oblique, extremity acutely angular, 

 and much above the line of the base; basal margin 

 regularly arcuate; epidermis olive-yellow, with very 

 oblique narrow rays; within bluish, tinged with violet 

 above, highly iridescent; cardinal teeth obtuse, smooth, 

 nearly obsolete; lateral teeth single in each valve. 



SYNONYMES. 



U. leptodon, Raf. Ann. gen. des Sc. Phys., vol. v. p. 295. 



Poulson's trans., p. 21. Say, Amer. Conch. No. 6. Ferr. 



Mag. de Zool. 

 U. planus, Barnes. Silliman's Journal, vol. vi. p. 272. 

 Anodonta purpurascens, Swainson. 

 Symphynota tenuissima, Lea. Trans. Amer. Philos. Soc, (new 



series,) vol. iii. p. 453, pi. xi. fig. 21. 

 Cab. A. N. S. No. 20406. 



OBSERVATIONS. 



This shell has an exterior much resembling that of 

 an Anodonta, but the teeth are generally sufficiently 

 developed to constitute it a true Unio. It is allied 

 to U.fragilis, but differs widely in the teeth, in being 

 pointed posteriorly, and in not being alated. It is 

 connate when perfect. 



Inhabits the Ouisconsin, Mr. Barnes. I found a 

 single specimen in Alabama. The specimen figured 

 is from the Scioto river, and was presented by Dr. 

 William Blanding. 



