62 DESCRIPTION OF NEW 



Diam. -8, Length 1*2, Breadth 2-1 inches. 



Shell elliptical, inequilateral, somewhat inflated, furnished with nu- 

 merous small folds on the posterior slope and side ; substance of the 

 shell thick before, and thinner behind ; beaks rather prominent ; liga- 

 ment short and light horn-coloured ; epidermis very dark green ; cardi- 

 nal teeth rather large, single in the right valve and double in the left; 

 lateral teeth rather short and straight ; anterior cicatrices distinct ; pos- 

 terior cicatrices confluent ; dorsal cicatrices situated on the base of the 

 cardinal teeth ; cavity of the shell rather deep ; cavity of the beak angu- 

 lar; nacre purple, rarely white. 



Remarks. — Among the shells recently sent by Dr Burrough from 

 Mexico, were many specimens of this species, which I believe not to 

 have been before described. It is remarkable for the numerous small 

 folds on the posterior slope, and these in some individuals extend over 

 the umbonial slope and posterior half of the side. In the old speci- 

 mens the posterior margin is disposed to be biangular, and the epider- 

 mis is quite black — in the younger it is dark green, and obscure raj'^s 

 may sometimes be observed. Among the specimens examined, two 

 were white in the nacre, and one of these salmon-coloured within the 

 beaks. The lateral teeth, where the beaks are eroded, are somewhat 

 curved. 



Unio Tappanianus. Plate XVII. fig. 55. 



Testa obovata, subinjiata, inmquilaterali, postic^ dilalata ; valvulis tenuibus ; natibus sub- 

 prominentibus, undulatisque ; epidermide fulvo-fuscd ; dentibus cardinalibus compressis cur- 

 visque; later alibus tenuis ; margarita subsalmonia. 



Shell obovale, rather inflated, inequilateral, dilated behind; valves thin; beaks 

 somewhat prominent and undulated; epidermis yellowish biown ; cardinal teeth com- 

 pressed and curved ; lateral teeth thin ; nacre somewhat salmon. 



U. viridis (Conrad), not Rafinesque. 



Hab. Juniata, near Hollidaysburg. Dr. Kirtland. 



Schuylkill, and a small stream near Lancaster. Mr Hyde. 



