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DESCRIPTION OF FIFTY-TWO SPECIES OF TJNIONID^. 



Proc. Acad. Nat. Sci., 1811, p. 192. 



Hab.—Ogeechee River, Liberty Co., Geo., Major John Le Conte. 



My cabinet and cabinet Academy Natural Sciences. 

 Diam. -8, • Length 1-1, Breadth 2-1 inches. 



Shell smooth, narrow elliptical, somewhat inflated, inequilateral, round before 

 and obtusely angular behind ; substance of the shell somewhat thick ; beaks a lit- 

 tle prominent and nearly terminal ; ligament rather short, rather thick and dark 

 brown ; epidermis brownish, very much rayed and with distant marks of growth ; 

 umbonial slope raised and obtusely angular ; posterior slope narrow elliptical and 

 raised into a small carina ; cardinal teeth small, compressed and crenulate ; lateral 

 teeth long, lamellar and somewhat curved; anterior cicatrices distinct, rather small 

 and well impressed; posterior cicatrices confluent, rather large and moderately im- 

 pressed ; dorsal cicatrices placed nearly in the centre of the cavity of the beaks ; 

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

 nacre white and iridescent. 



Remarks. — I owe to the kindness of my friend, the late Major John Le Conte, a 

 small suite of this species which some twenty years since he brought from Georgia. 

 For a long time I considered these specimens to belong to Geddingsianus (nobis) 

 from South Carolina. Having more recently given them a careful comparison 

 with that species, I have no longer any hesitation in separating them. It is a 

 smaller species, has a higher umbonial slope, is a little more transverse and has 

 more and closer rays. It need not be confounded with aquilus (nobis), from Geor- 

 gia, which is a more compressed species and is larger. The young specimens 

 show dehcate undulations at the tips of the beaks. 



Unio Stevensii. pi. 7, fig. 19. 



Testa bialata, valde plicata, triangular!, compressa, valde inaiquilaterali ; valvulis crassiuscalis, antice 

 crassioribus ; natibus vix prominentibus ; epidermide tenebroso-cornea, eradiata ; dentibus cardi- 

 nalibus parvis sulcatisque ; lateralibus longis, lamellatis subcurvisque ; raargarita alba et irides- 

 cente. 



Shell double winged, very much folded, triangular, compressed, very inequi- 

 lateral; valves somewhat thick, thicker before; beaks scarcely prominent; epi- 

 dermis dark horn color, without rays ; cardinal teeth small and sulcate ; lateral 

 teeth long, lamellar and somewhat curved ; nacre white and iridescent. 

 Proc. Acad. Nat. Sci., 1811, p. 188. 



Hah. Yuruari Elver, tributary to Essequebo Eiver, Guiana, E. P. Stevens. 



My cabinet and cabinet of C. M. Wheatley. 



