﻿I.AMPSILIS 71 



Margaron (UnioJ obtnsus Lii.v, Syti., 1852, p. 39; 1870, p. 62. 

 Unto pallescens Lea, Pr. Am. Phil. Soc, IV, 1845, P- ^64; Tr. 



Am. Phil. Soc, X, 1848, p. 79, pi. vii, fig. 20; Obs., IV, 



1848, p. 79, pi. VII, fig. 20. 

 Margaron (UnioJ pallescens Lka, Syn., 1852, p. 27; 1870, p. 



43- 



A solider shell than either Lampsilis hydiana or L. approx- 

 ima. It is more inflated than the latter and is never rayed 

 like the former. There are individual specimens, which are 

 intermediate and seem to more or less connect the three species. 



Lampsilis perpasta (Lea). 



Shell oibovate, solid, greatly inflated, with moderate beaks 

 and a rounded posterior ridge, which is somewhat double and 

 ends in a faint, narrow, biangulation at a considerable distance 

 above the base line of the shell ; ligament brown, carried for- 

 ward under the beaks and ending in front in a small lunule ; 

 growth lines rather rude, irregular ; epidermis shining tawny, 

 brownish at the beaks, rayless ; left valve with two stumpy 

 pseudocardinals, the hinder opposite the beak, and two re- 

 mote, heavy laterals, the lower the solider ; hinge line rounded 

 in the middle ; right valve with one principal pseudocardinal 

 and a smaller one in front and behind it ; beak cavities moder- 

 ately excavated ; muscle scars deep, smooth ; nacre whitish, 

 tinted with lurid purple behind. 



Length 50, height 35, diam. 28 mm. 



Length 55, height 42. diam. 35 mm. 



Type locality, Coosa River, Alabama. Also Swamp Creek, 

 Georgia. 

 Unio perpastiis Lea, Pr. Ac. N. Sci., Phila., V, 1861, p. 60; 



Jl. Ac. N. Sci. Phila., V, 1862, p. 69, pi. vii, fig. 219; Obs., 



VIII, 1862, p. 73, pi. VII, fig. 219. 

 Margaron (Unio) perpastiis Lea, Syn., 1870, p. 43. 

 Lampsilis perpastiis Simpson, Syn., 1900, p. 532. 



Since writing the Synopsis I have had an opportunity of 

 seeing quite a number of shells of this rare species. In that 

 work I placed it in the ventricosa group, but I am now in- 



