80 NEW UNIONID7E OF THE UNITED STATES. 



Unio roRPimtEUS. PI. 10, fig. 228. 



Testa kevi, elliptica, ventricosa, valde masquilaterali, postice obtuse biangulata, antice rotundata; valvulis 

 suberassis, antice crassioribus; natibus prominulis; epidermide rufo-fuscescente, micanti, eradiata; 

 dentibus cardinalibus crassiusculis, eorrugatis, crenulatis, in utroque valvulo duplieibus; lateralibus 

 longis, suberassis, eorrugatis subr'ectisque; margarita saturate-purpurea et valde iridescente. 



Shell smooth, elliptical, ventricose, very inequilateral, obtusely biangular behind, 

 rounded before; valves rather thick, thicker before; beaks somewhat prominent; 

 epidermis reddish brown, shining, without rays ; cardinal teeth rather thick, corru- 

 gate, crenulate, double in -both valves; lateral teeth long, somewhat thick, corrugate 

 and rather straight ; nacre deeply purple and very iridescent. 

 Proc. Acad. Nat. Sci. 1861, p. 60. 



jjah. — Coosa River, Alabama. E. R. Showalter, M. D. 

 My cabinet and cabinet of Dr. Showalter. 

 Di am . 1, Length 1-1, Breadth 1-8 inch. 



Shell smooth, elliptical, ventricose, very inequilateral, obtusely biangular behind, 

 rounded before ; substance of the shell rather thick, thicker before ; beaks somewhat 

 prominent; ligament rather long and somewhat thick; epidermis reddish brown, 

 shining, without rays, with distant dark lines of growth ; umbonial slope much raised 

 and rounded ; posterior slope regularly elliptical, slightly raised, very dark brown, 

 with an obscure groove from the beaks to the posterior margin ; cardinal teeth rather 

 thick, corrugate, crenulate, double in both valves ; lateral teeth long, rather thick, 

 corrugate and nearly straight ; anterior cicatrices distinct, small and deeply impressed ; 

 posterior cicatrices distinct, rather large and well impressed ; dorsal cicatrices in a row 

 above the cavity of the beaks and on the cardinal tooth ; cavity of the shell deep and 

 wide ; cavity of the beaks rather shallow and rounded ; nacre very deep purple and 

 very iridescent. 



Remarks. — As in many of the new species from Dr. Sowalter, I have but a single 

 imperfect one of this. It is very distinct from any I know, and is perhaps most nearly 

 allied in outline to umbrosus (nobis) and Lecontianus (nobis). It is a smaller species 

 than the former, more inflated, and of a much deeper color in the nacre, as well as in 

 the epidermis. It is also smaller than the latter, has a darker epidermis, and has a 

 deep purple nacre ; while Lecontianus has it usually white or very pale purple. It is 

 also more inflated. The specimen before me is very much eroded at the beaks and 

 upper part of the disk, so that we cannot have any idea of the undulations of the tips. 

 Young and perfect specimens would have a lighter epidermis, and may be found to 

 have rays, but this has no appearance of them. The nacre is intensely purple, even 

 more so than purpuratus, Lam., which cannot be confounded with this, as it is a much 

 larger species, is obovate and very much more inflated, and has a darker epidermis. 



