62 AMERICAN CORBICULAD-aS. 



Hah. North America, in New England, in the States of New York, New 

 Jersey, Pennsylvania, Ohio, Wisconsin, Michigan, Maryland and Virginia, 

 and in the St. Charles River at Quebec in Canada. (Cabinets of the Bos- 

 ton Society, the Academy of Natural Sciences of Philadelphia, Smithsonian 

 Institution, Jay, Prime, and others.) 



Telllna virginica, Gml., 1788, 3236, pi. clix, f. 15. 



Tellina pusitla (pars), Dillw. II, 1817, 106. 



Cyclas diibia, Sat, Nich. Encycl. 3d ed. 1819, f. 4, pi. i, f. x. 



Physemoda cequalis, Rafinesque, Ann. Gen. Sci. Phy. V, 1820, 319. 



Pisidium ahruptum, Haldeman, Proc. Acad. Nat. Sci. Phila. 1, 1841, 53. 



Pisidium duhiitm, Haldeman, loc. sub. cit. I, 1841, 103. 



Pisidium sequale, Rafinesque, Prime in Bost. Jour. VI, 1852, 367. 



Pisidium virf/inicum, Bourguignat, Amer. Malac. I, 1853, 53. 



Sphaerium dubium, Deshayes, Biv. Brit. Mus. 1854, 266. 



Pisum virginicum, Deshayes, loc. sub. cit. 1854, 281. 



Pisum ahruptum, Deshayes, loc. sub. cit. 1854, 281. 



Pisum dubium, Deshayes, loc. sub. cit. 1854, 282. 



Muscidiujii dubium, Adams, Rec. Gen. II, 1858, 451. 



Musculium abruptum, Adams, loc. sub. cit. II, 1858, 451. 



Musculium virginicum, Adams, loc. sub. cit. II, 1858, 452. 



This, the largest species of the genus found in America, is not 

 easily confounded with any other — its size, and general robust 

 and coarse appearance, rendering it at once distinct. The young 

 shell is more elongated and less full than the adult, and of a 

 lighter color. Found not unplentifully in running waters. 



Compared with P. adamsi, to which it bears some resemblance 

 in outline, it is larger, more robust, more produced on the anterior 

 side, less full, the beaks are larger, the markings on the surface 

 are heavier, and the color is darker. 



Its foreign analogue is P. amnicum, of Europe, to which it 

 is very closely allied ; it differs, however, in being somewhat 

 smaller and more oblique. 



Fig. 62. 



P, virginicum. 



