64 NEW UNIONID.E OF THE 



the shell rather deep ; cavity of the beaks small and rounded ; nacre purple and iri- 

 descent. 



Soft Parts. — Branchial riterus filled the whole length of the outer branchiae. Brcm- 

 chioe rather large, inner ones somewhat the larger, gently curved below, free two-thirds 

 of the length of abdominal sack. PaJpi small, subangular, united only a short distance 

 on the posterior edge. Mantle very thin, thicker on the margin. Branchial opening 

 rather large, with numerous small, brown papillae on the inner edge. Anal opening 

 with small brownish papillas on the edges. Super-anal opening long, without color, 

 and attached below for a short distance. Color of the mass whitish. 



Bemarks. — This species belongs to the group of which Lecontianus (nobis) may be 

 considered the type. It is rather more transverse, more oblique, not quite so oval, 

 and is darker in the epidermis. The nacre is usually more purple. I have not seen 

 it of any other color, while the Lecontianus is sometimes white and salmon as well as 

 purple. It has also some resemblance to rufusculus, (nobis,) but this species is more 

 quadrate, higher on the umbonial angle, and disposed to be white in the nacre. 



Unio rostriformis. pi. 10, fig. 4G. 



Testa la3vi, vald6 transversa, compressa, ad latere planulata, valde inequilaterali, postice acute acuminata; val- 



vulis tenuibus ; natibus vix prominulis, ad apices undulatis ; epidcrmide tencbroso fusca, obsolete radiata ; 



dontibus cardinalibus parvis, acuminatis, in utroque valvule duplicibus; lateralibus praclongis, lamoUatis 



rectisque : margarita subpurpurca et iridescente. 



Shell smooth, very transverse, compressed, flattened at the sides, very inequilateral, 



acutely pointed behind; valves thin ; beaks scarcely prominent, undulated at the 



tips ; epidermis dark brown, obscurely radiated ; cardinal teeth small, pointed and 



double in both valves ; lateral teeth very long, lamellar and straight ; nacre slightly 



purple and iridescent. 



Proc. Acad. Nat. Sci., 1856, p. 262. 



jffab. — Swift Creek, near Macon, Georgia. Bishop Elliott. 



My cabinet and cabinet of Bishop Elliott. 

 Diam. '4, Length -8, Breadth 2-3 inches. 



Shell smooth, very transverse, compressed, flattened at the side, very inequilateral, 

 acutely pointed behind and suddenly rounded before ; substance of the shell thin, 

 rather thicker in the interior ; beaks scarcely prominent, with a number of transverse 

 wrinkled undulations at the tip; ligament long and thin; epidermis dark brown, with 

 obscure rays on the posterior part and with distant marks of growth ; cardinal teeth 

 small, acuminate, crenulate, double in both valves ; lateral teeth very long, lamellar 

 and straight ; anterior cicatrices distinct, rather small ; posterior cicatrices confluent ; 

 dorsal cicatrices very small and placed on the inside of the plate posterior to the cardinal 

 tooth ; cavity of the shell exceedingly shallow ; cavity of the beaks very shallow and 

 scarcely angular ; nacre slightly purple or salmon and very iridescent. 



