UNITED STATES AND ARCTIC AMERICA. 189 



My cabinet and cabinet of Mr. Lesquareux, Columbus, Ohio. 

 Diana. 1-9, Length 2 ; 5, Breadth 3-2 inches. 



Shell smooth, oblique, much inflated, very inequilateral, rounded behind; sub- 

 stance of the shell very thick, somewhat thicker before ; beaks very prominent, 

 swollen, incurved and slightly undulate at the tips ; ligament large and dark brown ; 

 epidermis greenish olive, polished, very much rayed, with very distant marks of 

 growth ; umbonial slope raised and rounded ; posterior slope large, cordate, flattened, 

 with three indistinct raised lines from the beaks to the margin ; cardinal teeth 

 large, thick, erect, crenulate and double in both valves ; lateral teeth rather long, 

 very thick, oblique and nearly straight; anterior cicatrices distinct, very large and 

 very deeply impressed ; posterior cicatrices confluent, very large and moderately well 

 impressed ; dorsal cicatrices placed over the centre of the cavity of the beaks and 

 along the base of the cardinal tooth ; cavity of the shell deep and rounded ; cavity 

 of the beaks rather deep and obtusely angular ; nacre silvery white or tinted with 

 salmon and iridescent. 



Remarks. — I have seen but two specimens of this species, and they are both before 

 me. One is evidently full grown, the other is only about one-third grown. The 

 younger is of a fine salmon color in the cavity and the region of the teeth. This 

 species reminds one of two very different species, — ligamentinus, Lam., and ellipsis, 

 (nobis), — but it need not be confounded with either. The former is more elliptical, 

 and, while it is very much of the form of the latter, it has a finer surface of 

 epidermis and is more polished and fuller of greenish rays. It reminds one also of 

 orhiculatus, Hild., but it is greener, has more rays and is more inflated, and has 

 higher beaks. The younger specimen is covered with beautiful, closely-set green 

 rays over the whole disk, and the tips of the beaks, being nearly perfect, shew a 

 lew very small indistinct undulations at the tips. I name it after Mr. Frank 

 Higgins, who first procured it, and through the kindness of Mr. Moores it was sent 

 to me. 



Unio vestitus. PL 25, fig. 259. 



Testa kevi, clliptica, compressa, insequilaterali, postiee obtuse angulata, antiee rotunda; valvulis sub- 

 tenuibus, anticc paulisper crassioribus ; natibus prominulis ; epidermide vel lutea vel Iuteo-fusca, 

 polita, radiis obliquis viridis vestitis; dentibus cardinalibus parvis, conrpressis, aeumiuatis, crenu- 

 latis, in utroque valvulo duplicibus ; lateralibus sublongis, lamellatis, subobliquis corrugatisque ; 

 margarita. albida et splendida. iridescente. 



Shell smooth, elliptical, compressed, inequilateral, obtusely angular behind, round 

 before ; valves rather thin, a little thicker before ; beaks a little prominent ; epider- 

 mis yellow or yellowish brown, polished, covered with oblique greenish rays ; 

 cardinal teeth small, compressed, pointed, crenulate and double in both valves , 



