﻿LAMPSILIS 45 



Lampsilis ai<tilis (Conrad). 



Shell rather thin, suboval, ovate or subelliptical, but mod - 

 erately inflated ; beaks not prominent ; posterior ridge low, 

 rounded, sometimes faintly double, so that the shell is slightly 

 biangulate behind ; epidermis straw-color or yellowish-browu 

 to blackish, but smooth and rather shining, feebly rayed or 

 rayless ; hinge line with a single or double curve ; left valve 

 with two small, somewhat compressed pseudocardinals, one 

 in front of the other, both placed just in front of the beak, 

 and in the specimens seen, rather smooth, and two delicate, re- 

 mote laterals ; the central part of the hinge plate rounded ; 

 right valve with one pseudocardinal, sometimes with a feeble 

 second above it, and one rather high, truncated lateral ; beak 

 cavities moderately deep, conipressed ; muscle scars smooth, 

 rather shallow ; nacre whitish or lurid. 



Length 55, height 35, diam. 20 mm. 



Alabama River drainage; Little Red River, Clinton, Arkan- 

 sas? 



Type locality, Alabama River, Claiborne, Ala. 

 Unio altilis Conrad, New F. W. Shells, 1834, p. 43, pi. 11, fig. 



I, and p. 68. — Chenu, Bib. Conch., ist ser., Ill, 1845, P- ^i- 



pi. I, fig. I. 

 Margarita (Unio) altilis Lea, Syn., 1836, p. 24; 1838, p. 19. 

 Margaron (Unio) altilis Lea, Syn., 1852, p. 27 ; 1870, p. 42. 

 Lampsilis altilis Simpson, Syn., 1900, p. 529. 



In the few examples I have seen, the umbonal region is so 

 eroded that nothing can be made out regarding the character 

 of the beaks, which are probably not very full or high. The 

 species differs from L. cariosa generally in its darker epider- 

 mis, its smaller and thinner shell, in showing slight biangula- 

 tion behind and in the rather feeble post^basal swelling of the 

 female. Conrad says that the nacre is whitish and iridescent, 

 but all the specimens I have seen have a lurid nacre, often with 

 :a tinge of violet. 



