74 NEW UNIONID.E OF THE UNITED STATES. 



mide luteo-fusoescente, superne micanti, inferne striata, eradiata, ; dentibus cardinalibus parviusculis, 

 erectis, conicis corrugatisque ; lateralibus aublongis, lamellatis, corrugatis subcurvisque ; margarita 

 alba et iric 



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

 behind, obliquely rounded before ; valves somewhat thick, slightly thicker before ; 

 beaks somewhat prominent and inflated ; epidermis yellowish brown, shining above, 

 striate below, without rays; cardinal teeth rather small, erect, conical and roughened; 

 lateral teeth rather long, lamellar, roughened and slightly curved ; nacre white and 

 iridescent. 



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



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



My cabinet and cabinet of Dr. Showalter. 

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



Shell smooth, elliptical, ventricose, very inequilateral, obtusely angular behind, ob- 

 liquely rounded before; substance of the shell somewhat thick, a little thicker before; 

 beaks somewhat prominent and inflated ; ligament rather long, thick and chestnut 

 brown ; epidermis yellowish brown, shining above and striate below near the basal 

 maro-in, without rays, with obscure distant marks of growth ; umbonial slope very 

 much raised and rounded ; posterior slope regularly elliptical, slightly raised, yellowish, 

 with a broad slightly impressed groove from the beaks to the margin ; cardinal teeth 

 rather small, erect, conical, corrugate, and disposed to be double in the right as it is in 

 the left valve ; lateral teeth rather long, lamellar, corrugate and somewhat curved ; 

 anterior cicatrices distinct, moderately large and very deeply impressed ; posterior 

 cicatrices confluent, rather large and well impressed ; dorsal cicatrices placed above 

 the centre of the cavity of the beaks and along the ba.se of the cardinal teeth ; cavity of 

 the shell deep and regularly elliptical ; cavity of the beaks rather deep, wide and 

 angular ; nacre white and iridescent. 



RemarJcs. — Like several other new species from Dr. Showalter herein described, a 

 single specimen only was received. It is evidently an adult, and two inches wide, by 

 one and a half inches long. It is very much of the same outline as pallescens (nobis), 

 but is a very much smaller shell, more inflated, rather more oval and of a darker 

 epidermis. It is also very like to some varieties of cariosus, Say, but is more 

 inflated, particularly on the umbonial slope ; it is thicker in the substance of the 

 valves, and differs in the teeth. The specimen before me is much eroded, so that the 

 character of the beaks cannot be ascertained. The color of the epidermis is perhaps 

 darker than younger specimens will be found to be. No doubt young and perfect 

 specimens will prove to have bright yellow disks, and perhaps rays, which the speci- 

 men before me has not a trace of. 



