44 NEW UNIONID^, MELANIDyE, ETC.. 



Unio Leibii. PL 15, fig. 42. 



Testa Isevi, quadra, subcompressa, valde infequilaterali^ postice emarginata, antice rotundata; valvulis 

 subcrassis, antice crassioribus ; natibus subprominentibus, fere terminalibus ; epidermide straminea, 

 eradiata ; dentibus cardinalibus subgrandibus, erectis striatisque ; lateralibus curtis, rectis crassisque, 

 in utroque valvule duplicibus ; margarita alba et aliquanto iridescente. 



Shell smooth, quadrate, subcompressed, very inequilateral, eraarginate behind and 

 rounded before ; valves rather thick, thicker before ; beaks somewhat prominent and 

 nearly terminal ; epidermis straw yellow, eradiate ; cardinal teeth rather large, erect 

 and striate ; lateral teeth short, straight, thick and double in both valves ; nacre 

 white and slightly iridescent. 



Proc. Acad. Nat. Sci., 1862, p. 168. 



Hab.— Erie County, Michigan, G. C. Leib, M. D. . 



My cabinet and cabinet of the Smithsonian Institution. 

 Biam. -8, Length 1, Breadth 1-3 inches. 



Shell smooth, quadrate, subcompressed, very inequilateral, emarginate behind and 

 rounded before ; substance of the shell rather thick, thicker before ; beaks somewhat 

 prominent and nearly terminal ; epidermis straw yellow, without rays, with 

 numerous close lines of growth ; umbonial slope slightly raised and rounded ; 

 posterior slope raised into a high carina, almost a wing, and so impressed as 

 to form an emargination on the posterior margin ; cardinal teeth rather large, 

 erect, striate and disposed to be tripartite in the right valve; lateral teeth 

 short, straight, thick and double in both valves; anterior cicatrices distinct, 

 small and well impressed ; posterior cicatrices continent and very slightly impressed ; 

 dorsal cicatrices placed under the base of the cardinal tooth ; cavity of the shell 

 rather deep and round ; cavity of the beaks rather shallow and angular; nacre white 

 and slightly iridescent. 



Remarks. — Two odd valves only of this small species were among a number of 

 common species from the Michigan Zoological District. It is remarkably quadrate 

 in the outline. In these specimens the cardinal tooth is trifid in the right and 

 double in the left valve, and the lateral teeth double in both valves. But this may 

 not pervade all this species, as we find aberrations in the teeth of many of the 

 species. The outline of this shell is very unusual. It is remarkably quadrate, and 

 it is greatly to be regretted that perfect specimens of both valves were not in our 

 possession, better to describe its characteristics. I name it after Dr. Leib, who sent 

 it to the Smithsonian Institution. 



