216 DESCRIPTION OF 



Remarks. — Mr. Edgar procured this species when on a geological tour with 

 Professor Troost up the Holston River. A single specimen only is in my pos- 

 session, but its characters are so distinct that I do not hesitate to propose it as a 

 new species. It seems to be between U. undatus, (Barnes,) and V. Cor, (Con- 

 rad.) The specimen before me is remarkable for the broad rays extending to 

 the basal margin behind the umbonial slope on the flattened part of the side of 

 the valve. The beaks of the specimen being eroded, it is impossible to say if 

 the tips be undulated or not. 



Unio Boydianus. Plate 16, Fig. 32. 



Testa ohovatd, subinflatd, valdc inaquilaterali ; valvulis subtenuibus; natibus subprominenlibus, ad 

 apices undulatis; epidermide luteo fused; dentibus cardinalibus compressis ; lateralibus longis siibrec- 

 tisque; margaritd alba et iridescente. 



Shell obovate, rather inflated, very inequilateral ; valves rather thin ; beaks rather prominent, undulate at 

 the tip ; epidermis yellowish-brown ; cardinal teeth compressed ; lateral teeth long and nearly straight ; 

 nacre white and iridescent. 



Hab. Oak Orchard Creek, Orleans County, N. Y. Dr. Boyd. 

 My Cabinet, and Cabinet of Dr. Jay. 

 Diam. .8, Length 1.2, Breadth 1.9 inches. 



Shell obovate, rather inflated, very inequilateral, subangulate before, with re- 

 gular, rather close and nearly equidistant marks of growth; substance of the 

 shell rather thin, thicker before; beaks rather prominent, with small undula- 

 tions at the tip; ligament rather short and thin; epidermis yellowish-brown, 

 striate; cardinal teeth compressed, double in both valves; lateral teeth long and 

 nearly straight; anterior cicatrices distinct; posterior cicatrices confluent; dor- 

 sal cicatrices on the under side of the cardinal tooth; cavity of the shell rather 

 deep and rounded; cavity of the beaks shallow and subangular; nacre white 

 and iridescent. 



Remarks. — Dr. Jay kindly sent me two specimens of this shell some time 

 since. They were collected by Dr. Boyd, Assistant State Geologist. One of 

 them has a few rays behind, the other is without rays. The anterior slope in 

 both specimens is truncate, so much so in the smaller one, as to induce me to 

 believe it to be deformed. It is perhaps most nearly allied to U. ochraceus, Say. 



