﻿350 NEW UNIONID^) OF THE 



Unto perpictus. PL 58, fig. 175. 



Testa Isevi, elliptica, subinflita, valde inasquilaterali, postice obtuse biangulata, aotice rotundata ; valvulis 

 tenuibus, diaphanus, antice crassioribus ; natibus prominulis, ad apices undulatis; epidermide luteo- 

 oliva, subnitida, undique virido radiata ; dentibus cardinalibus parvis, erectis, conicis, crenulatis, in 

 utroque valvulo duplicibus ; lateralibus longis lamellatis rectisque ; margarita- cseruleo-alba et valde 

 iridescente. 



Shell smooth, elliptical, somewhat inflated, very inequilateral, obtusely biangular 

 behind and rounded before ; valves thin, diaphanous, thicker before ; beaks a little 

 prominent and undulate at the tips ; epidermis yellowish olive, somewhat shining, 

 with green rays all over ; cardinal teeth small, erect, conical, crenulate and double in 

 both valves ; lateral teeth long, lamellar and straight ; nacre bluish white and very 

 iridescent. 



Proo. Acad. Nat. Sci., 1860, p. 306. 



Hah. — Bull River, Tennessee, President Estabrook ; and Holston River, Dr. Troost. 



My cabinet. 

 Diam. *7, Length 1-2, Breadth 21 inches. 



Shell smooth, elliptical, somewhat inflated, very inequilateral, obtusely biangular 

 behind and rounded before ; substance of the shell thin, semitransparent, thicker 

 before; beaks a little prominent, with three or four undulations at the tips; liga- 

 ment rather long, thin and dark brown; epidermis yellowish olive, somewhat shining, 

 with green interrupted rays all over, and with rather distant marks of growth ; 

 umbonial slope slightly raised and rounded ; posterior slope slightly raised and with 

 numerous small rays ; cardinal teeth small, erect, conical, crenulate and double in 

 both valves, in the right valve very slightly so ; lateral teeth long, lamellar and 

 straight ; anterior cicatrices distinct and well impressed ; posterior cicatrices confluent 

 and very slightly impressed ; dorsal cicatrices situated on the under side of the plate ; 

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

 obtusely angular; nacre bluish white and very iridescent. 



Remarks. — There are three specimens before me, received a long time since from Pre- 

 sident Estabrook, of Knoxville, and Dr. Troost, of Nashville, Tenn. They then seemed 

 to me to belong either to Prevostianus (nobis), or to be a variety of iris (nobis); but 

 I am now satisfied that they differ specifically from both. It is more transverse than 

 the former and less so than the latter. Two of the specimens are young, and are 

 undulate at the tips. The third, which is figured, is a mature individual from Bull 

 river, and probably as large as it grows. It is somewhat like scitulus, herein described, 

 but it is a thinner shell, is more transverse and has the rays more close, more numer- 

 ous and more interrupted. It also reminds one of Novl-Eboraci (nobis), being nearly of 

 the same outline and with very much the same kind of rays. 



