78 NEW UNIONID.E OF THE 



pressed shell than falJax. None had beaks perfect enough so that tmdiUation.s 

 could be observed. 



Unio piNGuis. PL 15, fig. 58. 



Testa Iffivi, ellipticil, inflata, valde inaequilaterali ; valvulis subcrassis ; natibus promincntibus, retiorsis ; 

 epidermide lutea, obscure radiata et polita ; dentibus cardinalibus subgrandibus, in utroquc valvulo 

 duplicibus, acuminatis crenulatisque ; lateralibus magnis, lamellatis longis curvisque ; margarita alba et 

 iridescente. 

 Shell smooth, elliptical, intlated, very inequilateral ; valves rather thick ; beaks 

 prominent, recurved ; epidermis yellowish, obscurely radiated and polished ; cardinal 

 teeth rather large, double, pointed and crenulate ; lateral teeth large, lamellar, long 

 and curved ; nacre white and iridescent. 

 Proc. Acad. Nat. Sci., 1857, p. 8-1. 



Hah. — St. Peter's River, upper Mississippi. B. W. Budd, M. D. 



Cabinet of Dr. Budd. New York. 

 Diam. 1-3, Length 1-9, Breadth 2-7 inches. 



Shell smooth, elliptical, intlated, very inequilateral, angular anterior to the beaks ; 

 substance of the shell rather thick, thinner behind ; beaks prominent, incurved and 

 recurved; epidermis yellowish, darker towards the beaks, obscurely rayed and 

 shining ; ligament rather short and thick ; umbonial slope rounded and closely ap- 

 proaching the margin ; anterior slope very much contracted ; cardinal teeth rather 

 large, and double in both valves, pointed, crenulate, compressed and slightly curved ; 

 lateral teeth large, lamellar, long, curved, single in the right and double in the left 

 valve ; anterior cicatrices distinct, the superior one large and deeply impressed ; poste- 

 rior cicatrices confluent ; dorsal cicatrices placed within the cavity of the beak and on 

 the outside of the cardinal tooth ; palleal cicatrix well impressed ; cavity of the shell 

 deep and rounded ; cavity of the beaks deep and subangular ; nacre silvery white and 

 iridescent. 



Remarks. — A single specimen only was procured by Dr. Budd, and therefore the 

 diagnosis is necessarily made without a knowledge of any variations of form in other 

 individuals. It belongs to a group the type of which may be considered to be lega- 

 mentinus, Lam., [crctssxis, Say,) but it differs in being less ponderous and more inflated. 

 It is less cblique than that species and rather more rounded. It diflfers from another 

 of this group to which it is nearly allied, orbiculatus, Hild., in being thinner, more in- 

 flated and more regularly rounded at the anterior margin. The anterior lunule is 

 very wide, and a remarkable character is in the unusual swelling of the anterior por- 

 tion of the disks, the greatest transverse diameter being towards the anterior portion 

 of the shell. The cardinal teeth are remarkably erect and pointed, and the lateral 

 teeth very lamellar and abrupt at the posterior end. 



