40 ON THE NAIADES, 



Hab. Alabama River. Judge Tait. 



My Cabinet. 

 Diam. 1-1, Length 1-5, Breadth 1-5 inches. 



Shell subtriangular, thick, oblique, depressed anterior to umbonial 

 slope ; substance of the shell very thick anteriorly and thin posteriorly ; 

 beaks very thick and much elevated; epidermis dark brown and wrin- 

 kled ; cardinal teeth large, crenate and deeply cleft in the left valve, 

 and emerging from a pit in the right ; lateral teeth thick, slightly curved 

 and nearly parallel with the line of the cardinal teeth ; anterior cica- 

 trices distinct, the great one forming a deep pit ; posterior cicatrices 

 distinct, the smaller one being placed at the end of the lateral tooth ; 

 dorsal cicatrices situated on the plate between the cardinal and lateral 

 teeth ; cavity of the beaks shallow^ ; nacre pearly white. 



Remarks. — There is no species which this so closely resembles as 

 the scalenius (Rafin.). It is, however, less oblique and more expanded 

 along the posterior basal margin, and the posterior margin forms a more 

 obtuse angle. It is with great pleasure I name it after my fi'iend, 

 Judge Tait of Claiborne, Alabama, to whom science is greatly indebted 

 for his exertions in making known the natural history of his vicinity. 



Unio lacteolus. Plate VIII. fig. 19. 



Testa ellipticd, transversd, insequilaterali, subivjlatu ; valvulis subcrassis ; nati- 

 bus radiatis, plicis brevibus ; dentibits cardinalibiis in valvidd ulrdqve diiplicibus 

 longisque ; lateralibus longis, a cardinalibus separaiis ; margarild lacteold. 



Shell elliptical, transverse, inequilateral, somewhat inflated ; valves not thick ; beaks 

 having short radiating folds; cardinal teeth long and double in both valves ; lateral 

 teeth long and separate from the cardinal teeth ; nacre pearly and milk white. 



Hab. Rio de la Plata. 



My Cabinet. 



Cabinet of the Academy of Natural Sciences of Philadelphia. 



Cabinet of W. Hyde. 



Unio delodonta? Lam. 



