﻿CYI'ROGENIA 327 



nearer the anterior end, curved forward over the lunule and 

 having very feeble sculpture ; posterior ridge well developed, 

 high and narrowly rounded at the umbonal region, with a 

 shallow, radial groove in front of and another behind it ; 

 surface having strong, low, concentric ridges, each ridge some- 

 times equaling a season's growth ; sometimes they are more 

 numerous ; in addition to this it is more or less covered with 

 irregular knobs or tubercles ; epidermis pale greenish-yellow 

 covered with a pattern of rich green flecks or dots, which 

 shows a tendency to form rays ; left valve with two strong, 

 low, ragged pseudocardinals and two laterals ; right valve 

 with one pseudocardinal and one double lateral ; hinge plate 

 wide and flat ; beak cavities rather shallow, compressed ; mus- 

 cle scars small, deep ; nacre silvery, white or flesh-colored, 

 thicker in front. 



Length 55, height 50, diam. 35 mm. 



Length 42, height 47, diam. 30 mm. 



Ohio, Cumberland and Tennessee River systems ; St. Francis 

 and Saline Rivers, Arkansas? Eastern Iowa? The specimens 

 reported from the western localities may be C. aberti. 



Type locality, Ohio. 

 Unio irroraHus Le^v, Tr. -\m. Phil. Soc, IH, 1830, p. 269, pi. 



V, fig. 5; Obs., I, 1834, p. II, pi. V, fig. 5. — Hanley, Biv. 



Shells, 1843, P- 181, pi. XX, fig. 25. — Chenu, 111. Conch., 



1858, pi. X, figs. 3, ^a, T,b. — Reeve, Conch., Icon., XVI, 1864, 



pi. xii, fig. 44. 

 Margarita (Unio) irroratiis Lea, Syn., 1836, p. 16; 1838, p. 15. 

 Margaron (Unio) irroratiis Lea, Syn., 1852, p. 22 ; 1870, p. 34. 

 Unio irrorata Deshayes, Encyc. Meth., II, 1830, p. 579. 

 Thelidcnna irrorata Swainson, Tr. on Mai., 1840, p. 271, 



fig- 540- 

 Cyprogenia irrorata Simpson, Syn., 1900, p. 610. — Ortm.vnn, 



Ann. Car. Mus., VIII, 1912, p. 312, fig. 17. 

 Unio verrncosiis albus HiLDREn'H, Am. Jl. Sci., XIV, 1828. p. 



281. 



