﻿ii8 i.AMi'sn.is 



ranged ; left valve with two subcompressed pseudocardinals 

 and two nearly straig-ht, delicate laterals ; rigfht valve with one 

 pseudocardinal and a faint one above it, with sometimes a 

 slight tooth behind, and a single lateral ; beak cavities shallow, 

 compressed ; anterior muscle scars shallow ; posterior scars very 

 faint ; nacre bluish-white, iridescent behind, slightly thicker in 

 front. Male shell generally a little rhomboid, the posterior 

 point being rarely biangulate and generally not greatly elevated 

 above the base line, though sometimes it is midway up ; female 

 shell with a feebly developed, rounded marsupial swelling. 



Length 55, height 30, diam. 15 mm. 



Warren County, Kentucky ; Clinch River, Tennessee ; Tus- 

 cumbia, Alabama. 



Type locality, Tuscumbia, Ala. 

 Unio planicostatits Li^\, Pr. .Ac. N. Sci. Phila., IV, i860, p. 92; 



Jl. Ac. N. Sci. Phila., IV, i860, p. 354, pi. ux, fig. 179; Obs.. 



VIII, i860, p. 36, pi. ux, fig. 179.. 

 Margaron (Unio) plank ostatus Lea, Syn., 1870, p. 43. 

 Lampsilis planicostatus Simpson, Syn., 1900, p. 553. 



I am doubtful whether this is more than a mere variety of 

 L. iris. It seems to be generally more compressed and wider 

 behind ; the males are more rhomboid as a rule, and the mar- 

 supial swelling is less developed than in that species. 



Lampsilis nebulosa (Conrad). 



Shell irreo-ularly long elliptical or subrhomboid, subcompress- 

 ed to subinflated; beaks scarcely full, their sculpture consisting 

 of a few, irregular, slightly doubly-looped ridges ; surface with 

 irregular growth lines, greenish-yellow with narrow to wide, 

 generally broken, rays, sometimes almost rayless ; left valve 

 with two somewhat compressed pseudocardinals and two near- 

 ly straight laterals: right valve with two pseudocardinals. the 

 upper the smaller, and one lateral ; beak cavities shallow ; pos- 

 terior .scars faint to distinct; nacre bluish-white, sometimes 

 with pinkish or pun>le center, iridescent and slightly thinner 

 behind. Male shell subrhomboid, the posterior i>oint often 



