AND DESCRIPTIONS OF NEW SPECIES. 71 



brought by Prof. Vanuxem from the western states. It is very nearly 

 allied to the plicatus (Lesueur) in its general characteristics, but when 

 the beaks are not much eroded, it may be at once distinguished from 

 that species by the numerous small irregular undulations which sur- 

 round and cover the beaks, and of which the plicaliis is entirely destitute 

 except at the very tip of the beaks ; where the small folds are entirely 

 unconnected with the large ones. In a very young state no two 

 species, scarcely, can be more diflferent, the muUiplicatus being entirely 

 covered with undulations, while the plicatus possesses none, except 

 the small ones at the tip. In this state it resembles exceedingly the 

 tuherculatus of Barnes, and when I received my first specimen, I 

 referred it to that species, considering it a variety, and should most 

 probably have continued to be of that opinion, had I not obtained a 

 large specimen sufficiently perfect to display the irregular undulations 

 in the region of the beaks. The facts mentioned above, show the 

 absolute necessity of studying the young in making ourselves acquainted 

 with the species. 



Unio Asperrimus. Plate V. fig 



»• 



Testa sebquadrangulari, inaquilaterali, postice biangulari, natibus ad baseos 

 marginem sulcata et 7iodiilis instructd; valvulis percrassis ; natibus elevatis; dentibus 

 cardinalibus prcsgrandibus, lateralibus magnis subredisque ; margaritd pulchrd et 

 iridescente. 



Shell sub-quadrangular, inequilateral, biangular behind,- sulcated from beaks 

 to basal margin, thick and noduled ; valves very thick ; beaks elevated ; cardinal 

 teeth very large ; lateral teeth large and nearly straight ; nacre beautifully pearly 

 and iridescent. 



Hab. Ohio River. T. G. Lea. 



My Cabinet. 



Cabinet of T. G. Lea. 



Cabinet of Lyceum of Natural History of New York. 



Diam. 2-3, Length 3-6, Breadth 4-8 inches. 



Shell sub-quadrangular, biangular behind, sulcated from beak to 



