OF THE GENUS UNIO. 267 



cavity of the beaks shallow — nacre salmon colour and irides- 

 cent ; colour stronger under the beaks, from which beautiful 

 fine rays diverge to the margin. 



Remarks. — This species, which I have seen only in Tar 

 River, N. C, approaches more closely to the unio picto- 

 rum of Europe than any yet discovered in this country. 

 When I first found it, I felt assured it was the same ; but 

 upon closer examination and comparison find it to be essen- 

 tially different. The cavity of the beak is much less and the 

 cardinal tooth shorter and more lobed. 



3. Unio Donacipormis. Plate IV. fig. 3. 



Testa ineBquilaterali, transversa, cuneata, rugata ; dente cardinali pro- 

 minente ; umbonibus postice angulatis ; margine dorsali posteriori sub- 

 carinatd. 



Shell inequilateral, transverse, cuneiform, wrinkled ; cardinal tooth 

 very prominent ; beaks angular behind ; posterior dorsal margin subca- 

 rinate. 



Hab. Ohio. T. G. Lea. 



My Cabinet. 

 Diam. -7, Length 1-0, Breadth 1-5 inches. 



Shell not very thick, rounded before and pointed behind — 

 substance of the shell not thick — ^beaks slightly elevated, not 

 decorticated, almost touching ; angulated by an oblique carina 

 passing from the beaks to the posterior margin ; this causes a 

 slight concavity from the beaks towards the posterior mar- 

 gin — ^ligament passing to the point of the beaks — dorsal and 

 posterior dorsal margins slightly curved, the latter sub-cari- 

 nate ; posterior margin acutely angulai* ; posterior basal mar- 

 gin nearly straight ; basal margin curved ,• anterior and ante- 

 rior dorsal and basal margins rounded — epidermis olive, with 

 green rays diverging from the beaks to all parts of the mar- 

 gin; surface glabrous and slightly wrinkled; has distinct 



