46 NEW UNIONIDiE, MELANID^, ETC., 



RemarTis. — There were two specimens of this species received, with a single one 

 of acutissimus, from Dr. Showalter, and at first sight I was disposed to think it a 

 strong variety only of that shell, but on examining the soft parts, I found a female 

 which had a Avell charged branchial uterus, differing very much in the form and 

 position of the branchial ovisacks from that shell. The acutissimus has many more 

 sacks, and they extend nearly the whole breadth of the outer branchise. In the 

 parvulvs they are placed in the middle, and occupy not more than one-third the 

 breadth. The thick posterior edges of the mantle were also much darker. The 

 enveloping hard part differs from acutissimus in being greenish and not salmon- 

 colored, while the ejaidermis agrees in the form of the minute angular spots. In 

 outline it is much like Conradius, having the same folds on the posterior slope, but 

 differs in the epidermis, not having rays like that species. It evidently belongs to 

 that group which includes the small species acntissimxts, Conradius, penicillatus and 

 rubellinus, and the cicatrix on the lower edge of the foot shows it is furnished with 

 a hyssus like others of this little group. 



Unio perpurpueeus. pi. 16, fig. 44. 



Testa Isevi, elliptica, subinflata, inEequilaterali, postice et antice rotundata ; valvulis subcrassis, antice 

 crassioribus ; natibus prominulis ; epidermide tenebroso-viridi, nigricente, radiis capillaris ; dentibus 

 cardinalibus parviusculis, erectis, conicis, in utroque valvulo duplicibus, striatis ; lateralibus longis 

 rectisque ; margarita valde purpurea et iridescente. 



Shell smooth, elliptical, somewhat inflated, inequilateral, rounded behind and 

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

 dark green inclining to black, with capillary rays ; cardinal teeth rather small, erect, 

 conical, double in both valves and striate ; lateral teeth long and straight ; nacre 

 very purple and iridescent. 



Proc. Acad. Nat. Sci., 1861, p. 41. 



Hah. — Tennesse, J. G. Anthony. 



My cabinet and cabinets of the Academy of Natural Sciences and Mr. Anthony. 

 Diam. -57, Length -97, Breadth 1-62 inches. 



Shell smooth, oblong, somewhat compressed, flattened at the side, nearly equilate- 

 ral, obtusely angular behind, round before; substance of the shell rather thin, 

 slightly thicker before; beaks slightly prominent; ligament rather small and dark 

 brown ; epidermis dark green, inclining to black, with numerous capillary rays on 

 the posterior portion ; umbonial slope slightly raised and rounded ; posterior slope 

 rather small, very dark, with two obscure impressed lines on each valve from the 

 beaks to the posterior margin ; cardinal teeth rather small, erect, conical, double in 

 both valves and striate ; lateral teeth long, straight and somewhat corrugate ; 



