CHIEFLY OF THE UNITED STATES. 315 



epidermis blackish, without rays, with rather distant marks of growth ; umbonial 

 slope raised and rounded; posterior slope narrow elliptical, slightly carinate ; 

 cardinal teeth small, erect, somewhat compressed and crenulate ; lateral teeth rather 

 long and slightly curved; anterior cicatrices distinct, small and well impressed; 

 dorsal cicatrices placed across the centre of the cavity of the beaks ; cavity of the 

 shell rather deep and wide ; cavity of the beaks shallow and obtusely angular ; nacre 

 purple and iridescent. 



Eemarks.— Quite a number of this little purple-nacred species, with its black 

 epidermis, was sent to me by Major Downie. It belongs to the group of which 

 parvus, Barnes, may be considered the type. It more closely resembles glans (nobis) 

 on one side and iMuhis on the other. The epidermis is black, like jjaulus, but it may 

 be distinguished by being less transverse and in not having a white nacre. From 

 glans it may be distinguished by being less solid, less ventricose, and having a deeper 

 purple nacre. Every one of the specimens before me has the disk entirely of a deep 

 purple, except the anterior basal margin, which is not quite white, being along the 

 edge of a pale purple. 



TJmo vALLATus. PI. 50, fig. 128. 



Testa nodulosa, rotundata, lenticulari, subiuflata, inaiquilaterali; valvulis crassis, antice erassioribus ; 

 natibus subprominentibus ; epidermide luteo-fusca, eradiata ; dentibus cardinalibus pergrandibus, 

 elevatis granulatisque ; lateralibus crassis, curtis et obliquis ; margarita argentea et iridescente. 



Shell nodulous, rounded, lenticular, somewhat inflated, inequilateral; valves 

 thick, thicker before; beaks somewhat prominent; epidermis yellowish-brown, 

 without rays ; cardinal teeth very large, raised and granulate ; lateral teeth thick, 

 short and oblique; nacre silver-white and iridescent. 

 Proc. Acad. Nat. Sci. 1868, p. 145. 



Hah. — Alabama River, Dr. Sho waiter. 



My cabinet and cabinet of Dr. Showalter. 

 ^''''™- ^■^' Length 2-1, Breadth 2-3 inches. 



Shell nodulous, rounded, lenticular, somewhat inflated, inequilateral; substance of 

 the shell thick, thicker before; beaks somewhat prominent; ligament short, thick 

 and light brown ; epidermis yellowish-brown, without rays, with rather close lines of 

 growth; umbonial slope raised and rounded; posterior slope subcordate, slightly 

 carinate, furnished with curved rows of nodules; cardinal teeth very large, raised 

 and granulate; lateral teeth thick, short and oblique; anterior cicatrices distinct, 

 large and deeply impressed; posterior cicatrices distinct, large and well 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 very deep and angular; nacre 

 silver-white and iridescent. 



T5 



