﻿68 r.AMPSiLis 



the pattern of rays is holder, more (Hstitict, and more hriUiant. 

 It seems to replace Z,. luteoh in the waters of the southwestern 

 states. The nacre of L. hydiana is scarcely thickened in front, 

 while in lutcola it generally becomes thicker anteriorly. 



Lampsilis approxima (Lea). 



Shell but slig-htly thickened, long elliptical or long obovate,. 

 somewhat inflated ; the surface faintly concentrically sculptured, 

 but shining ; beaks not very high or full ; epidermis straw-color, 

 often tawny in the region of the beaks, usually rayless except 

 at the posterior slope, and when there are rays they are al- 

 ways faint ; right valve with two pseudocardinals, the upper 

 somewhat compressed and smaller ; left valve with two pseudo- 

 cardinals ; there is one lamellar, curved lateral in the right valve 

 and two in the left ; beak cavities rather shallow ; anterior mus- 

 cle scars well impressed ; posterior scars large but rather faint ; 

 nacre whitish or bluish, sometimes dirty, pale purplish, usuall)'' 

 with lurid, bronzy blotches in the cavity of the shell, very 

 slightly thickened in front. Male shell sometimes feebly bian- 

 gulate behind, but not pointed; female shell considerably swol- 

 len at the post-base and rounded or sub-truncate behind. 



Length (male) 80, height 47, diam. 26 mm. 



Length (female) 70. height 57, diam. 26 mm. 



Southern Louisiana ; southern Alabama. 



Type locality. Red River, Alexandria, La. 

 Unio approximus Lea, Pr. Am. Phil. Soc, IV, 1845, p. 164; 



Tr. Am. Phil. Soc. X, 1848, p. 74, pi. v, fig. 13; Obs., IV, 



1848, p. 48, pi. V, fig. 13. 

 Margaron (Unio) approximus Lea, Syn., 1852, p. 28; 1870, 



p. 44. 

 Lampsilis approximus Simpson, Syn., 1900, p. 537. 

 Unio ailinis Lea, Pr. Am. Phil. Soc, V, 1852, p. 251 ; Tr. Am. 



Phil. Soc, 1855, p. 271, pi. XIX, fig. 26; Obs.. V, 1852, p. 27. 



pi. XIX, fig. 26. 

 Marp:aron (Unio) affinis Lea, Syn.. 1852. p. 27; 1870. p. 42. 

 Lampsilis affinis Simpson, Syn., 1900, p. 537. 



