﻿LAMPSirjS 113 



part of the shell, slightly shining; left valve with two pseudo- 

 cardinals, the anterior larger, and two delicate, nearly straight 

 laterals ; right valve with two pseudocardinals, the lower 

 larger, and one lateral ; nacre bluish-white, tinted with purple 

 in the center, or purplish throughout, scarcely thickened in 

 front. Male shell somewhat rhomboid, the posterior point 

 nearest to the base ; female with a long, rather full marsupial 

 swelling, slightly biangulate behind, the biangulation midway 

 up from the base or a little higher. 



Length (male) 45, height 23 mm. 



Length (female) 40, height 23, diam. 15 mm. 



Length (female) 43, height 26, diam. 17 mm. 



Current and Little Red Rivers, Arkansas. 



Type locality, Current River, Ark. 

 Unio occidentalis Conrad, Monog., VII, 1836, p. 64, pi. xxxvi, 



fig- I. 

 Margaron (Unio) occidentalis Lea, Syn., 1852, p. t,t^ ; 1870, p. 



53- 



Lampsilis occidentalis Simpson, Syn., 1900, p. 551. 



I have seen a half dozen female shells which I presume are 

 the above species, but I have never seen a male shell. The 

 largest specimen is dark and feebly rayed. It is probable that 

 none of them are quite fully grown. These shells are from the 

 Little Red River, Arkansas. They are something like female 

 L. concestator or nnicostata, but are smaller and more delicate. 



Lamp.sius nigrrrima (Lea). 



Shell obovate, rather thin to subsoiid, subcompressed, with 

 a scarcely developed posterior ridge ; rounded in front ; rounded 

 or feebly bianulate behind ; beaks not inflated, sculptured with 

 fine, slightly doubly-looped ridges ; surface with irregular 

 growth lines ; epidermis greenish-yellow to blackish, when fresh 

 rather dull and cloth-like but becoming smoother and shining 

 when rubbed, sometimes feebly rayed behind ; hinge line gen- 

 erally evenly curved; left valve with two compressed pseudo- 

 cardinals, the anterior higher, and two slightly curved, lamellar 

 laterals ; right valve with two pseudocardinals, the lower much 



