I'XITED .STATES. 15 



Remarks. — A single specimen only, a female, is before me. The branchial uterus 

 was charged the whole width with ova not matured, so that the embryonic form could 

 not be described. In outline this species is near to famatus (nobis) and suhflavus 

 (nobis) as well as to (leloilontus, Lam. It is larger and even darker than the first. 

 It is also allied to Plantii (nobis), but is not so regularly elliptical and not so much 

 impressed. It differs also in the color of the epidermis, the Plantii being of a dark 

 chestnut color. 



Unio obfuscus. pi. 22, fig. 80. 



Tcstfi lacvi, rcgulariter clliptica, inflata, posticc rotundatii, inequilatcrali ; valvulis subtcuuibus; iiatibus 

 subprominentibus ; epidermidc tenebroso-fusca, obsolete radiata, subpolita; dentibus cardinalibus 

 subcompressis, crenulatis, in utroque valvule duplicibus ; lateralibus lamellatis, sublongis subcurvisque ; 

 margarita paulisper sahnonis et valdfe iridescente. 



Shell smooth, regularly elliptical, inflated, rounded behind, inequilateral; valves 

 rather thin; beaks somewhat prominent; epidermis dark brown, obscurely rayed and 

 somewhat polished; cardinal teeth rather compressed, crenulate, double in both 

 valves ; lateral teeth lamellar, rather long and somewhat curved ; nacre light salmon 

 color and very iridescent. 



I'roc. Acad. Nat. Sci., 1857, p. 172. 



Hah. — Flint River, near Macon, Georgia. J. C. Plant. 



My cabinet and cabinet of Mr. Plant. 

 Diam. -6, Length -9, Breadth 1*6 inches. 



Shell smooth, regularly elliptical, inflated, rounded behind, striate and somewhat 

 sulcate before ; substance of the shell rather thin ; beaks somewhar prominent ; liga- 

 ment rather short, thin and dark brown ; epidermis dark brown, obscurely rayed, 

 somewhat polished and with distant marks of growth; umbonial slope slightly raised 

 and rounded ; cardinal teeth rather compres.sed, crenulate, erect and double in both 

 valves; lateral teeth lamellar, rather long and somewhat curved ; anterior cicatrices 

 distinct and well impressed ; posterior cicatrices confluent ; dorsal cicatrices situated 

 nearly across the centre of the cavity of the beaks ; cavity of the shell rather deep 

 and rounded; cavity of the beaks rather deep and subangular; nacre light salmon 

 color and very iridescent. 



Soft Partx. — Branchial uterm not charged, but ova were found in the ovarium. 

 Branchia; large, nearly semicircular, inner one much the larger, oblique at posterior 

 margin, united to the abdominal sack the whole length. Palpi rather large, suboval, 

 united on the posterior edges. Mantle very thin, thickened and colored on the inferior 

 border. Branchial opening large, with numerous brownish papillfeon the inner edges. 

 Super-anal opening smaXX, slightly colored on the iinier edges and united below. Color 

 of the mass whitish. 



Remarks. — Two .specimens only of this small species were received. The smaller 



