﻿UNITED STATES AND NORTHERN MEXICO. 351 



Unto Lindsleyi. PI. 58, fig. 176. 



Testa laevi, elliptica, compressa, ad latere planulata, valde' insequilaterali, postice subbiangulata, antice 

 oblique rotundata ; valvulis subcrassis, antice crassioribus ; natibus prominulis; epidermide vel lutea 

 vel luteo-oliva, micante, undiqu£ virido maculata ; dentibus cardinalibus parviusculis, compresso-conicis 

 crenulatisque ; lateralibus longis, crassis curvisque ; margarita alba et iridescente. 



Shell smooth, elliptical, compressed, flattened at the sides, very inequilateral, sub- 

 biangular behind, obliquely rounded before ; valves rather thick, thicker before ; beaks 

 slightly prominent ; epidermis yellow or yellowish, olive, shining, spotted with green 

 all over; cardinal teeth rather small, compressed-conical and crenulate; lateral teeth 

 long, thick and curved ; nacre white and iridescent. 

 Proc. Acad. Nat. Sci. 1860, p. 306. 



Hah. — Tennessee. President Lindsley. 



My cabinet and cabinet of President Lindsley. 

 Diam. -8, Length 1-5, Breadth 2-5 inches. 



Shell smooth, elliptical, compressed, flattened at the sides, very inequilateral, sub- 

 biangular behind, obliquely rounded before ; substance of the shell rather thick, 

 thicker before ; beaks slightly prominent ; epidermis yellow or yellowish olive, shining, 

 spotted with green all over and with rather distant lines of growth ; ligament long 

 and dark brown ; umbonial slope low and flattened ; posterior slope very slightly 

 carinate ; cardinal teeth rather small, compressed-conical, crenulate and disposed to 

 be double in the right as it is in the left valve ; lateral teeth long, thick, curved, 

 much thickened at the posterior end ; anterior cicatrices distinct and well impressed ; 

 posterior cicatrices confluent and well impressed ; dorsal cicatrices placed in a row 

 above the centre of the cavity of the beaks; cavity of the shell very shallow and 

 wide ; cavity of the beaks shallow and obtusely angular ; nacre white and iridescent. 



Remarks. — I have four specimens of this species before me from President Lindsley, ■ 

 of Nashville, but I do not know from what river they were taken in Tennessee. It 

 is a very remarkable species, and perhaps the finest of the group of which pictus 

 (nobis) may be considered the type, and to which Menhianus (nobis) and interruphis 

 (nobis) belong. It differs from pictus in being a stouter shell, is not so broad behind 

 nor is it so high in the posterior slope. In the green quadrate spots, which are so 

 remarkable and so beautiful in both species, it differs in having them smaller and 

 perhaps in their being more square. These spots are at the crossing of the rays at 

 the lines of growth, the rays being pale or indistinct from the beaks to the margin. 

 In both there is a slight emargination on the upper portion of the posterior margin. It 

 may at once be distinguished from interruptus and Menhianus by these two species 

 having broad green rays, which, though partly interrupted by spots, have the rays 

 distinct from the beaks to the margin. One of the four specimens is inclined to put 

 on a yellowish tint in the cavity of the beaks. Neither have the beaks perfect 



