218 ON THE NAIADES, 



Diam. '8, Length 1-3, Breadth 2-1 inches. 



Shell reversely ovate, very inequilateral, slightly inflated, rather 

 straight on the basal margin and elevated on the posterior dorsal mar- 

 gin ; substance of the shell thin ; beaks slightly elevated ; ligament long 

 and narrow^ ; epidermis dark brown and rather smooth ; anterior and 

 posterior cicatrices confluent; dorsal cicatrices situated in the cavity of 

 the beaks ; cavity of the shell wide and rather deep ; cavity of the 

 beaks very shallow ; nacre purple. 



Remarks. — To the kindness of Dr Burrough I am indebted for the 

 privilege of describing this species. It is with pleasure I take the op- 

 portunity of placing his name upon it. It was procured by him near 

 the city of Manilla. It resembles, in outline and colour, the Unio 

 cuprinus (nobis), but has no trace of teeth. It is most remarkable 

 perhaps for its deep colour. 



Margaritana* Raveneliana. Plate XVII. fig. 50. 



Tesld subcylindraced, valde transversd et insequilaterali, inflatd; valvulis tenui- 

 bus; natibus exiguis ; dentibus cardinalibus parvis, subcompressis ; margaritd 

 caruleo-albd. 



Shell subcylindrical, very transverse, inequilateral, inflated ; valves thin ; beaks 

 small ; cardinal teeth small, rather compressed ; nacre bluish white. 



Hab. French Broad and Swananoe rivers. North Carolina. 



My Cabinet. 

 Cabinet of Dr Ravenel. 

 Diam. -9, Length 1-1, Breadth 2-2 inches. 



Shell subcylindrical, very transverse, inequilateral, inflated, disposed 

 to be compressed near the basal margin, where it is often emarginate; 

 substance of the shell thin; beaks small; ligament rather short; epi- 

 dermis brown, with rays on the posterior part; umbonial slope large, 

 rounded ; cardinal teeth consisting in each valve of a small compressed 



* See note, ante page 43. 



