PLEUROBEMA ar 
oped, narrowly rounded, ending in a blunt point below the 
median line; epidermis scarcely smooth, reddish-brown; pseu- 
docardinals triangular, two in the left and one to three in the 
right valve; beak cavities shallow; muscle scars rather small, 
impressed ; nacre whitish, thinner behind. 
Length 33, height 27, diam. 22 mm. 
Length 32, height 24, diam. 17.5 mm. 
Black Warrior and Cahawba Rivers, Alabama. 
Type locality, Black Warrior River, near its source. 
Unio rubellus Conrav, New F. W. Shells, 1834, p. 38, pl. vr, 
fig. 2—CHENU, Bib. Conch., rst ser., III, 1845, p. 20, pl. 11, 
fig. 2. 
Margarita (Unio) rubellus Lea, Syn., 1836, p. 33; 1838, p. 28. 
Margaron (Unio) rubellus Lea, Syn., 1852, p. 34; 1870, p. 
Pleurobema rubella Simpson, Syn., 1900, p. 757. 
Unio rudis Conrad, Monog., No. 9, 1837, p. 76, pl. XLiIl, fig. I. 
Unio pulvinulus Lea, Pr. Am. Phil. Soc., IV, 1845, p. 164; Tr. 
Mitieee mike Oe, Sy loio. pO: Ot, pl. vill, fic. 24; Obs., EV; 
1945; ps 55, pl. viti, ig: 24: 
Margaron (Unio) pulvinulus Lua, Syn., 1852, p. 26; 1870, p. 
Al. 
[ have before me a large number of shells from the above 
two rivers that agree in all essential characters with Conrad’s 
Umo rubellus. It is a small, very solid, inflated form with a 
reddish-brown, rayless, almost rough epidermis, and_ with 
white nacre in all the examples I have seen. 
ot 
on 
PLEUROBEMA FURVUM (Conrad). 
Shell somewhat obovate, solid, subinflated or inflated, in- 
equilateral; beaks rather full and high; anterior end a little 
narrowed and rounded; base line curved, fullest just behind 
the middle; outline of dorsal slope rounded, sometimes raised 
almost to an angle at the hinder end of the ligament ; posterior 
ridge rounded, ending in a point at or below the median line; 
surface with uneven, concentric sculpture; epidermis reddish- 
brown, dark brown or nearly black with very fine, crowded, 
concentric wrinkles, dull to subshining; pseudocardinals tri- 
