﻿144 i,AMi;siMS 



terior slope ; left valve with two ragged pseudocardinals, the 

 anterior higlier and subcompressed, posterior low and feebly 

 developed, with two nearly straight laterals ; right valve with 

 one pseudocardinal and a faint one above it, with two laterals, 

 the lower smaller but well developed ; beak cavities very shal- 

 low, with a few small scars; muscle scars small, somewhat im- 

 pressed ; nacre brilliant, silvery and iridescent, especially be- 

 hind, and having a rather bluish tint. 



Length 35, height 21, diam. 15 mm. 



Type locality. Lake Monroe, Florida. 

 Unio trossulus Lea, Desc. 12 sp. Uniones, 1843; Tr. Am. 



Phil. Soc., IX, 1846, p. 278, pi. XL, fig. 6; Obs., IV, 1848, 



p. 36, pi. XL, fig. 6.— Simpson, Pr. U. S. Nat. Mus., XV, 



1892, p. 427, pi. LXVIII, fig. 3. 

 Margaron (Unio) trossulus Lea, Syn., 1852, p. 25 ; 1870, p. 39. 

 Lampsilis trossulus Simpson, Syn., 1900, p. 562. 



I have seen no shell but the type that I can refer with cer- 

 tainty to this species. This specimen is probably a rather young 

 male shell and resembles the bright male specimens of amygdor- 

 lum in some respects. But it is much soHder, the hinge is 

 heavier and straighter, and the beaks are more anterior. It 

 seems strange if it is a valid species that the numerous collec- 

 tions made in Lake Monroe should not contain other specimens. 

 There are examples which seem to stand between this and 

 amygdaluui. 



Lampsilis pellucida (Lea). 



Shell very thin, obovate, rather compressed to slightly in- 

 flated, smooth, inequilateral, the posterior ridge full and round- 

 •ed ; beaks not high, with fine, somewhat doubly-looped ridges ; 

 surface smoky brown, with numerous undulating, faint rays ; 

 pseudocardinals two in the left valve, the hinder smaller, and 

 one in the right, with a vestige of a second above it. all com- 

 pressed ; two laterals in each valve, the ujiper in the right valve 

 very faint, all of them delicate and but feebly developed ; an- 

 terior muscle scars distinct ; posterior scars confluent ; nacre 

 bluish-white, iridescent. The figure of the type represents a 



