NEW UNIONIDiE OF THE UNITED STATES. 61 



Shell smooth, oblong, subcompressed, flattened at the side, swollen and biangular 

 behind, very inequilateral ; substance of the shell rather thick ; beaks prominent, 

 slightly pointed ; ligament long, thin and brown ; epidermis blackish, striate, without 

 rays, with rather distant marks of growth ; umbonial slope swollen and subbiangular; 

 posterior slope narrow, slightly raised, with slightly impressed lines on each valve 

 from the beaks to the margin; cardinal teeth rather small, crenulate, striate, disposed 

 to be double in both valves ; lateral teeth very long, somewhat curved, lamellate and 

 corrugate ; anterior cicatrices distinct, very large and well impressed ; posterior cica- 

 trices confluent, large and well impressed ; dorsal cicatrices placed nearly in the centre 

 of the cavity of the beaks; cavity of the shell wide and shallow; cavity of the beaks 

 very shallow ; nacre purple or salmon color and iridescent. 



Remarhs. — In outline this species is very near to Roanolcensis, (nobis,) but it is 

 much smaller and more inflated. It belongs to the group of which camplanatus is the 

 type. In one of the specimens before me there is a well defined cicatrix of the attach- 

 ment of a ventral muscle, like that in trapezoides, but it is more anterior. 



Uivio purus. PI. 4, fig. 209. 



Testa laevi, elliptica, subcompressa, postice rotundata, inxquilaterali ; valvulis suberassis, antice spissatis; 

 natibus subprominentibus ; epidermide luteo-oliva, glabra, ad umbones polita, obsolete radiata; dentibus 

 cardinalibus subgrandibus, acuminatis, crenulatis, in utroque valvulo subduplieibus; lateralibus sub- 

 longis, lamellatis subcurvisque ; margarita alba et iridescente. 



Shell smooth, elliptical, rather compressed, rounded behind, inequilateral ; valves 

 rather thick, thickened before ; beaks rather prominent ; epidermis yellowish-olive, 

 smooth, polished towards the beaks, obsoletely radiate ; cardinal teeth rather large, 

 pointed, crenulate and double in both valves ; lateral teeth rather long, lamellar and 

 somewhat curved; nacre white and iridescent. 

 Proe. Acad. Nat. Sci. 1858, p. 41. 



ffab. — Neuse River, six miles from Raleigh, N. C. Prof. Emmons. 



My cabinet and cabinet of Prof. Emmons. 

 Diam. -8, Length, 1-5, Breadth, 2-G inch. 



Shell smooth, elliptical, rather compressed, flattened at the sides, rounded behind, 

 inequilateral; substance of the shell rather thick, thickened before; beaks rather 

 prominent; ligament rather short, thick, brownish ; epidermis yellowish-olive, smooth, 

 polished towards the beaks, obscurely rayed; umbonial slope swollen and sub- 

 biangular; posterior slope rather wide and slightly raised; cardinal teeth rather large, 

 pointed, crenulate and double in both valves; lateral teeth rather long, lamellar and 

 somewhat curved; anterior cicatrices distinct, somewhat large and well impressed; 

 posterior cicatrices confluent, large and slightly impressed; dorsal cicatrices placed 



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