﻿tAMPSIIvIS 139 



sometimes blended together; left valve with two subcompressed 

 pseudocardinals, the anterior much the higher ; right valve 

 with two pseudocardinals, the upper very small and lamellar 

 and one lateral; beak cavities shallow, with two or three dorsal 

 pits ; nacre whitish, bluish-white, brownish or lurid purplish, 

 scarcely thicker in front. Male shell evenly elliptical or slight- 

 ly rhomboid, rounded or faintly biangulate behind ; female shell 

 rounded behind with only a very small marsupial inflation. 



Length 55, height 32, diam. 20 mm. 



Southwest Georgia. 



Type locality, Columbus, Ga. 

 Unio dispar Lea, Pr. Ac. N. Sci. Phila., IV, i860, p. 305 ; Jl. 



Ac. N. Sci. Phila., IV, i860, p. 327, pi. li, fig. 153; Obs., 



VIII, i860, p. 9, pi. 1,1, fig. 153. 

 Mar gar on (Unio) dispar Lea, Syn., 1870, p. 45. 

 Lampsilis dispar Simpson, Syn., 1900, p. 561. 



This species is close to L. vibex, but is generally smaller and 

 a little solider, the marsupial swelling is less developed, and it 

 is darker posteriorly than that species. 



Group of Lampsilis amygdaium. 



Shell rather small, obovate, inflated, epidermis varying from 

 smooth and shining to somewhat cloth-like, ashy-green or black- 

 ish, but always showing green tints when seen through trans- 

 mitted light, indistinctly rayed ; beaks rather hig'h, sculptured 

 with fine, parallel bars, arranged in a double loop, that in front 

 being larg-e and rounded, that behind small and rather pointed 

 below ; hinge teeth compressed ; nacre iridescent behind. The 

 greatest height of the shell is just behind the center ; its great- 

 est diameter is just in front of it, or at a point just behind the 

 "beaks ; the posterior end is often pointed and sonnewhat raised. 

 Animal having the marsupium large, reaching far below the 

 inner gills, and having a black border ; inner gills united to the 

 abdominal sac throug'hout ; anal opening smooth or only slig'htly 

 crenulate. 



