214 ON THE NAIADES, 



or some of its tributaries. This species has somewhat the characters 

 of the ohesus (nobis), and the compktnatus (Solander). It is not so 

 much inflated as the former, and is more so than the latter. My oldest 

 specimen is subemarginate on the basal margin. In all those procured 

 by Dr Blanding, the beaks were much eroded. 



Unio ca3iei,us. Plate XV. fig. 45. 



Testa, subtriangulari, insequilaterali, complanatd per umbones a natibus usque 

 ad marginem inferiorem ; valvuUs crassis ; radiis sparsis capillaribusque ; denfe 

 cardinali parvo, laterali magna, crasso, curvato ; murgarita alba. 



Shell subtriangular, inequilateral, flattened over the umbones from the beaks to the 

 basal margin ; valves thick ; rays scattered and capillary ; cardinal teeth small ; lateral 

 teeth large, thick and curved ; nacre white. 



Hab. Ohio river. T. G. Lea. 



My Cabinet. 

 Diam. 1-4, Length 2-3, Breadth 3-4 inches. 



Shell subtriangular, inequilateral, angular behind, flattened over the 

 umbones from the beaks to the basal margin ; substance of the shell 

 thick ; ligament thick ; epidermis yellow brown, with capillary rays ; 

 cardinal teeth small ; lateral teeth very large, thick and curved ; ante- 

 rior and posterior cicatrices both distinct ; dorsal cicatrices situated on 

 the inferior part of the cardinal teeth; cavity of the shell shallow, 

 welted ; cavity of the beaks very shallow. 



Remarks. — This species seems to possess partly the characters of 

 the gihbosiis (Barnes), and partly those of the planulatus (nobis). It 

 may be distinguished from them by its high dorsal margin, its very 

 remarkably thick lateral tooth and its capillary rays. 



