25 

 UNIO PECTOROSUS. 



Plate XI.— Fig. 1. 

 DESCRIPTION. 



Shell elliptical, inflated, moderately thick, yellow- 

 ish or olive, with unequal green rays, the larger rays 

 having distant dark spots; anterior side compressed, 

 extremity acutely rounded; ligament margin parallel 

 with the base; umbonial slope angular; umbo broad, 

 prominent, summit obtusely rounded; beaks distant 

 from the anterior extremity; within white, with a 

 wide greenish margin; cardinal teeth thick, promi- 

 nent, direct; cardinal plate dilated. 



SYNONYME. 



U. pectorosus, Nob. New fresh water shells, p. 37. pi. vi. fig. 1. 



May, 1834. 

 U. perdix, Lea. Trans. Amer. Philos. Soc. new series, vol. v. 



p. 72. pi. xi. fig. 31. Sept. 1834. 

 Cab. Jl. N. S. No. 2102. 



OBSERVATIONS. 



This shell has so nearly the outline of U.fasciolus, 

 that I have figured both on the same plate for com- 

 parison. It differs from that species in the rays, 

 dilated cardinal plate, &c. It is allied to U. ovatus, 

 Say, but is much more elongated. The specimen re- 

 presented has double cardinal teeth in each valve, but 

 the character is not permanent. It is in the splendid 

 collection of Mr. Poulson, and was found in the Har- 

 peth river, Tennessee. I obtained a few specimens 



