﻿122 f.AMPSir.lS 



IvAMi'SiMS AMCENA (Lea). 



Shell long elliptical, the dorsal and ventral lines nearly par- 

 allel, having the anterior and posterior ends rounded, subsolid, 

 subintlated, without a dorsal ridge ; beaks low, their sculpture 

 not seen, growth lines irregular ; surface greenish-yellow, more 

 or less wavy-rayed ; left valve with two equal, rather small 

 pseudocardinals and two laterals ; right valve with one pseudo- 

 cardinal, with a faint second one above it, and one lateral ; mus- 

 cle scars well impressed ; nacre bluish-white, silvery, sometimes 

 dark in the center, much thinner and iridescent behind. Fe- 

 male shell apparently smaller than the male, and more evenly 

 rounded behind, straight or very slightly incurved along the 

 base in front of the moderately developed, rounded marsupial 

 swelling. 



Length (male) 60, height 35, diam. 20 mm. 



Length (female) 50, height 2y, diam. 16 mm. 



Type locality, Holston River, Tennessee. 

 Unio amocnus Lea, Pr. Am. Phil. Soc., I, 1840, p. 286; Tr. Am. 



I^hil. Soc, VIII, 1842, p. 200, pi. X, fig. 12; Obs., Ill, 1842, 



p. 38, pi. X, fig. 12. — Hanley, Biv. Shells, 1856, p. 386, pi. 



XXIV, fig. 9. — Chenu, 111. Conch., 1858, pi. xxxiii, figs. 5, 



5a, 5/^. — SowERnv, Conch. Icon., XVI, 1868, pi. lxxix, fig. 



416. 

 Margaron (Unio) amoenus Lea, Syn., 1852, p. 29 ; 1870, p. 45. 

 Lampsilis amocnus Simpson, Syn., 1900, p. 555. 



I am not certain that this is more than a variety of L. nebu- 

 losa, but it is more oblong, the ends being nearly evenly round- 

 ed, while nchnlosa is pointed behind. 



Lampsilis tenera (Lea) 



Shell long elliptical or slightly obovate. subcompressed, sub- 

 solid, feebly biangulate and showing a nearly evenly rounded 

 outline behind ; beaks low but utterly eroded away in all the 

 specimens seen; surface with irregular growth lines, dirty 

 greenish-yellow or tawny, with a few- faint rays, sometimes 

 almost rayless ; left valve with two small pseudocardinals and 

 two delicate laterals ; right valve with one pseudocardinal and 



