FRESHWATER AND LAND SHELLS. 97 



Anodonta angulata. Plate XVI. fig. 52. 



Testd obovata, snbinjlata, valdi inatquilaterali ; valvulis subtenuibus, naiibus subpromi- 

 nulis ; clivo umboniali carinato ; epidermide luteold, subradiata ; margariia alba. 



Shell obovate, rather inflated, very inequilateral ; valves rather thin ; beaks some- 

 what prominent; umbonial slope carinate; epidermis yellow, somewhat radiated; na- 

 cre white. 



Hab. Lewis's Kiver. Professor Nuttall. 



My Cabinet. 

 Diam. -8, Length 1-1, Breadth 2-4 inches. 



Shell obovate, rather inflated, flattened before and behind the um- 

 bonial slope, very inequilateral; substance of the shell rather thin; 

 beaks somewhat prominent; umbonial slope acutely carinate; epider- 

 mis yellow, obscurely radiated on the posterior slope dark green ; an- 

 terior cicatrices distinct ; posterior cicatrices confluent ; dorsal cicatrices 

 placed in the centre of the cavity of the beaks; cavity of the shell 

 rather deep and angular ; cavity of the beaks shallow ; nacre white. 



Remarks. — A single valve, and that with a small fracture, of this 

 species was brought by Professor Nuttall. It is very peculiar iu pos- 

 sessing a carinate umbonial slope, and might, on account of this cha- 

 racter, at first sight be mistaken for a wide specimen of Margaritana 

 marginata. In this individual the cavity of the beak is salmon colour, 

 but this may not be a permanent character. The anterior margin 

 being small, and the posterior one large, gives it the outline of a Modiola. 



Among the shells of this family brought from the Columbia River 

 by this distinguished traveller and naturalist, were several specimens 

 of Margaritana margaritifera. To find that this species inhabits the 

 waters flowing into the Pacific, is of peculiar interest. Its being com- 

 mon to the European rivers and those of the United States flowing 

 into the Atlantic, gave it an importance in regard to its geographical 

 VI. — z 



