^j NEW UN'IONID.E OF THE 



Shell smooth, elliptical, slightly inflated, compressed behind, very inequilateral ; 

 substance of the shell rather thin, thicker before ; beaks slightly prominent, concen- 

 trically undulate at the tips ; ligament small, thin and yellowish brown ; epidermis 

 dark brown, obsoletely radiate and with distant marks of growth ; umbonial slope 

 slightly raised and obtusely angular ; posterior slope very slightly raised, with two 

 dark lines on each valve from the beaks to the posterior margin ; cardinal teeth small, 

 erect, acuminate, crenulate and double in both valves; lateral teeth long, lamellar 

 and somewhat curved ; anterior cicatrices distinct, small and somewhat impressed '■> 

 posterior cicatrices confluent and slightly impressed ; dorsal cicatrices placed across 

 the cavity of the beaks, cavity of the shell small and wide ; cavity of the beaks very 

 shallow and obtusely angular ; nacre white and very iridescent. 



Remarks. — Several specimens were in the collection brought by Capt. Pope. This 

 species is nearly allied to i^anntrS, Bar,, but it is more compressed, of a finer and 

 smoother epidermis, and the undulations of the beaks are smaller and more numerous, 

 the beaks being nearer to the anterior margin. The figure is made from a female, 

 and it is possible that it may prove to be female of Texasensk, described in this paper. 

 A large male specimen from Mr. Anthony for examination was labelled '• Mississippi." 



Anodonta Lewisii. pi. 02, fig. 187. 



Testa lajvi, elliptica, .subveutricosa, inaequilaterali, posdce obtuse angulata, antic6 rotundata ; valvulis sub- 

 ten uibus ; natibus prominulis, ad apice.f rugoso undulata ; epidermide tenebrosa-olivacea, cradiata ; 

 margarita Cffiruleo alba et iridesceiite. 



Shell smooth, elliptical, subventricose, inequilateral, obtusely angular behind and 

 rounded before ; valves rather thin ; beaks a little prominent, roughly undulate at 

 the tips ; epidermis dark olive, eradiate ; nacre bluish white and iridescent. 

 Proc. Acad. Nat. Sci. 1857, p. 84. 



Hab. — Erie Canal and Mohawk River, Herkimer County, N. Y., James Lewis, 

 M. D. ; and Genesee River, below Rochester, Prof. C. Dewey. 



My cabinet and cabinets of Dr. Lewis and Prof. Dewey. 

 Diam. I'l, Length 1-7, Breadth 3-2 inches. 



Shell smooth, elliptical, rather inflated, inequilateral, obtusely angular behind and 

 obliquely rounded before ; substance of the shell rather thin, very slightly thickened 

 on the anterior basal margin ; beaks a little prominent, roughly undulate in a double 

 series at the tips ; ligament rather long, somewhat thick and dark brown ; epidermis 

 dark olive, without rays or very obscurely rayed, with very distant marks of growth ; 

 umbonial slope raised and rounded ; posterior slope raised into a well defined carina, 

 with two impressed lines on each valve from the beaks to the margin ; anterior cica- 

 trices confluent, large, slightly impressed ; posterior cicatrices confluent very large 

 and very slightly impressed; dorsal cicatrices placed in the centre of the cavity of the 



