CHIEFLY OF THE UNITED STATES. 295 



terior slope sulcate, but nearly free from festoons ; cardinal teeth compressed, erect, 

 crenulate, somewhat tripartite in the right and double in the left valve ; anterior 

 cicatrices distinct and well impressed; posterior cicatrices confluent and slightly 

 impressed ; dorsal cicatrices placed above the centre of the cavity of the beaks ; 

 cavity of the shell rather deep and wide; cavity of the beaks rather deep and 

 angular; nacre whitish and iridescent. 



Remarks. — Two specimens only were received, both of the same size, color and 

 form. This species is nearly of the same outline with U. cyrenoides, Phil., but diflfers 

 in not being granulate nor solid, nor quite so deltoid. It cannot be confounded with 

 Neiucomhii (nobis), for that shell is rotund, solid and more compressed. But like the 

 latter it has transverse furrows, which are slightly interrupted by minute and 

 irregular festoon-like curves in the epidermis, and which give the surface a somewhat 

 roughened crinkled aspect. I have given the name encarpus to this species from these 

 festoon-like strife which pervade the disk. The posterior slopie has two impressed 

 lines on each valve, and the area within these lines is striate, not sulcate. 



Unio Gabbiantjs. pi, 43, fig. 106. 



Testa sulcata, triangulata, subinflata, aliquanto incBquivalva, insequilaterali, postice acute angulari, 

 antice oblique truncata ; valvulis crassiusculis, antice aliquanto erassioribus ; natibus prominenti- 

 bus, ad apices retusis ; epidermide tenebroso-olivacea, obsolete radiata ; dentibus cardiualibus 

 erectis, compressis et valde crenulatis ; lateralibus curtis, obliquis striatisque ; margarita argeutea 

 et iridescente. 



Shell sulcate, triangular, somewhat inflated, slightly inequivalve, inequilateral, 

 acutely angular behind, obliquely truncate before ; valves rather thick, somewhat 

 thicker before ; beaks prominent, drawn back at the tips ; epidermis dark oliv^e, 

 obscurely radiate ; cardinal teeth erect, compressed, and very much crenulate ; lateral 

 teeth short, oblique and striate ; nacre silver-white and iridescent. 

 Proc. Acad. Nat. Sci. 1868, p. 95. 



Hah. — Lake Nicaragua, Central America, Col. E. Jewett and Mr. W. M. Gabb. 



My cabinet and cabinets of Acad. Nat. Sci, and Col. Jewett. 

 Diam. -7, Length 1, Breadth 1-3 inch. 



Shell sulcate, triangular, somewhat inflated, slightly inequivalve, inequilateral, 

 acutely angular behind, obliquely truncate before; substance of the shell rather 

 thick, somewhat thicker before ; beaks prominent, drawn back and pointed at the 

 tijjs; ligament short, thin and light brown; epidermis dark olive, obscurely radiate; 

 umbonial slope obtusely angular ; posterior slope very slightly raised, regularly 

 elliptical; cardinal teeth erect, compressed and very much crenulate; lateral teeth 

 short, oblique and striate ; anterior cicatrices distinct and well impressed ; posterior 

 cicatrices distinct and moderately impressed ; dorsal cicatrices placed under the 



