2(i NEW UNIONID^ OF THE 



which I have dissected, that I have regarded it with great interest, and have 

 endeavored to describe it with care. At my request it was examined with great 

 minuteness by that excellent anatomist, my friend, Dr. Leidy, who pronounced this 

 to be its normal character. I cannot yet, however, help feeling some misgiving as to 

 its being a malformation, although in every respect the parts seem to be regular and 

 present no appearance of cicatrices, as they would if the adhesion had been caused 

 by a wound. In outline this specimen, which is figured, closely resembles the female 

 oifallax (nobis), but it is more rounded and not quite so large. It differs too in the 

 color of the epidermis, which is a deep olive brown, while fallax is a bright reddish 

 brown. The specimen figured is the female described. I subsequently received some 

 males, without the soft parts, which present a very regular ellipse. One from Mr. Pos- 

 tell is in fine condition, and measures one and one-sixteenth inches wide. 



Unio spissus. pi. 25, fig. 89. 



Testa liEvi, elHptica, siibventricosS, postic^ obtusfi angulata, subsequilatcrali ; valvulis crapsis; natlbns 

 prominulis; epidermide striata, rufo-fusca, obsolete radiata; dcntibus cardinalibus raagnis, crcctis, 

 compressis, crenulatis, in utroque valvulo subduplicibus ; lateralibus longis, crassis subcurvisque ; 

 margarita vel purpurea vel salmonis colore tincta at iridescente. 



Shell smooth, elliptical, rather ventricose, obtusely angular behind, nearly equilat- 

 eral; valves thick; beaks somewhat prominent; epidermis striate, reddish brown, 

 obsoletely radiated: cardinal teeth large, erect, compressed, crenulate, disposed to be 

 double in both valves ; lateral teeth long, thick and somewhat curved ; nacre either 

 purple or salmon color and iridescent. 



Proc. Acad. Nat. Sci., 1859, p. 112. 



Eab. — Satilla River, Wayne County, Georgia. T. C. Downie. 



My cabinet and cabinet of Mr. Downie. 

 Diam. 1-6, Length 2, Breadth 3-1 inches. 



Shell smooth, elliptical, rather ventricose, obtusely angular behind, nearly equilat- 

 eral ; substance of the shell thick ; beaks somewhat prominent ; ligament short, thick 

 and dark brown ; epidermis reddish brown, obscurely rayed, striate on the inferior 

 half and smooth and shining above ; umbonial slope very much raised, and obtusely 

 angular; posterior slope very wide, roughly striate, with two raised rather large 

 lines passing from beaks to posterior margin on each valve ; cardinal teeth large, 

 erect, compressed, crenulate, disposed to be double in both valves ; lateral teeth long, 

 very thick and somewhat curved ; anterior cicatrices distinct and well impressed ; 

 posterior cicatrices confluent, large ; dorsal cicatrices placed above the centre of the 

 cavity of the beaks ; cavity of the shell deep and rounded ; cavity of the beaks 

 somewhat deep and subangular ; nacre either ])uri)l(' or salmon color and 

 iridescent. 



i 



