UNITED STATES. G9 



(loiiMe lateral tooth is remarkable for having the lower division very much enlarged 

 towards the posterior end, while the upper division in the specimen before me is 

 very small, quite acioular and pointed, indeed almost obsolete. 



Unio ptriformis. pi. 12, fig, 50. 



Testa l«vi, obliquii, ovitbrmif?, valde compressa, valdc insequilaterali, po.sticc biangulata ; valvulis subcrassis, 

 antice crassioribus ; natibus subprominentibus ; epidermide luteo-eastanea, nitida, eradiata; dentibus 

 cardinalibus subgrandibus crenulatisf(uc ; lateralibu.s siibbrevibus subcurvisque ; margarita vel salmon is 

 colore tincta vol alba et iridescente. 

 Shell smooth, oblique, oviform, very much compressed, very inequilateral, biangu- 

 lar behind ; valves rather thick, thicker before ; beaks a little pi'ominent ; epidermis 

 yellowish chestnut color, polished, rayless; cardinal teeth rather large and crenulate; 

 lateral teeth rather short and somewhat curved ; nacre usually salmon color, some- 

 times whitish and iridescent. 



Proe. Acad. Nat. Sci., 1857, p. 31. 

 Eah. — Near Columbus, Georgia. Bishop Elliott. 

 My cabinet and cabinet of Bishop Elliott. 

 Diam. -6, Length 1-3, Breadth 21 inches. 



Shell smooth, oblique, oviform, very much compressed, very inequilateral, biangu- 

 lar behind and rounded before ; substance of the shell rather thick, thicker before ; 

 beaks a little prominent, situated towards the anterior margin ; ligament short and 

 somewhat thick ; epidermis yellowish chestnut color, polished, rayless, with distant 

 lines of growth ; umbonial slope flattened ; cardinal teeth rather large, crenulate, dis- 

 posed to be double in both valves ; lateral teeth rather short, somewhat curved, 

 with rather a broad plate between the lateral and cardinal teeth ; anterior cicatrices 

 distinct and deeply impressed ; posterior cicatrices distinct and well impressed ; dorsal 

 cicatrices well impressed and nearly in the centre of the cavity of the beaks ; cavity 

 of the shell very shallow ; cavity of the beaks very shallow and rounded ; nacre 

 usually pale salmon color, sometimes whitish, iridescent. 



Soft Birts. — Branchial uteriis. — There was no appearance of ova in the branchial 

 ovisacks, but the ovarium was filled with immature ones. BrancJiice large, semi- 

 circular, inner ones somewhat the largei-, free nearly the whole length of abdominal 

 sack. Palpi large, oval, attached at the upper portion of the posterior edges. Mantle 

 thin, thickened at the margin. Branchial opening small, with numerous small brown- 

 ish papillce. Ayial opening small, with very small brownish papilljE. Super-anal 

 opening rather small, united below for a short distance. Color of the mass whitish. 



Remarhs. — A number of specimens are before me from Bishop Elliott. This species is 

 remarkable for its ovate outline, being somewhat pear-shape. It is nearest to argenteus, 

 (nobis,) but is rather more oblique, has a more yellowish epidermis and is never, I 

 believe, silver white in the nacre like that species. I have seen no specimens with 



18 



