﻿136 l.AMl'Sll.lS 



front one hig'hcr and larger, and two almost straig'ht, delicate 

 laterals: ris^^ht valve with a single pseudocardinal and a vestige 

 of one above it, with one lateral ; beak cavities not deep ; an- 

 terior scars shallow, posterior scars scarcely visible ; nacre blu- 

 ish-white, often brownish or purplish in the center, iridescent 

 behind. The male shell is very slightly rhomboid, sometimes 

 feebly biangulate posteriorly, but generally rounded ; the female 

 is scarcely produced at the post-basal region and is round 

 behind. 



Length (male) 50, height 28, diam. 16 mm. 



Length (female) 48, height 29, diam. 15 mm. 



Type locality, Buckhead Creek and Tobesaufke Creek, Ma- 

 con, Ga. 



Unio gracilior Lea, Pr. Ac. N. Sci. Phil., VIH, 1856, p. 262. 

 Unto gracillior Lea. Jl. Ac. N. Sci. Phila., TV, 1858, p. 56, pL 



viiT, fig. 38; Obs., VL 1858, p. 56, pi. VIII. fig. 38. 

 Margaron (Unto) gracilior Lea, Syn., 1870, p. 45. 

 Lanipsilis gracilior Simpson, Syn., 1900, p. 559. 

 Unio obfuscus Lea, Pr. Ac. N. Sci. Phila., IX, 1857, p. 172 ; Jl. 



Ac. N. Sci. Phila., IV, 1859, p. 197, pi. xxii, fig. 80; Obs.,. 



VII, 1859, p. 15, p'l. xxn, fig. 80. 

 Margaron (Unio) obfuscus Lea, Syn., 1870, p. 45. 



Close to L. znbex, but generally thinner, smaller, less rayed 

 and more delicate. 



Lampsilis viBEX (Courad). 



Shell varying from thin to sub.solid, and from subcompressed 

 to considerably inflated, long elliptical or lotig obovate ; beaks 

 scarcely inflated or elevated, sculptured with a few doubly- 

 looped ridges ; growth lines irregular, often slightly sulcate ; 

 surface smooth and shining, tawny or greenish-yellow, usually 

 having wide, wavy rays, which may cover the entire shell or 

 only the posterior part of it. occasionally nearly rayless : left 

 valve with two somewhat compressed pseudocardinals. the 

 anterior the higher and longer, and two deli'catc, rather short 

 laterals : right valve with one pseudocardinal and a vestigial 



