786 PIL.KUROBEMA 
that species, but has a duller, more brownish epidermis, which 
sometimes shows the rest periods quite plainly. It is also more 
inflated and a little solider than that shell. 
Group of Pleurobema argenteum. 
Shell solid, oval to rhomboid, generally compressed, with 
high but not inflated beaks, well removed from the anterior 
end, which have strong, irregular sculpture, curved up and 
swollen behind where the bars are slightly looped; epidermis 
brownish to straw-color, sometimes having a few broken, 
blotched rays; teeth strong; cicatrices deep and distinct. Ani- 
mal unknown. 
PLEUROBEMA SIMULANS (Lea). 
Shell somewhat rhomboid, subcompressed, inequilateral, sub- 
solid ; beaks moderately full and high; posterior ridge well de- 
veloped, narrowly rounded, ending in a blunt point near the 
base of the shell; anterior end rounded; base line lightly 
curved; outline of the dorsal slope curved and raised into an 
angle behind the ligament, surface rather smooth; epidermis 
brownish-green or greenish-brown, sometimes faintly rayed 
or clouded with yellow ; left valve with two triangular pseudo- 
cardinals and two curved laterals; right valve with one pseudo- 
cardinal and vestiges of one or two others, with one double 
lateral; beak cavities not deep; muscle scars small; nacre blu- 
ish-white, thinner and very iridescent behind. 
Length 40, height 25, diam. 15 mm. 
Black Warrior and Cahawba rivers, Alabama; Pine Barren 
Creek, Escambia County, Florida. 
Type locality, Cahawba River, Shelby Co., Ala. 
Unio simulans Lea, Pr. Ac. N. Sci. Phila., I, 1871, p. 190; Jl. 
Ac, N, ‘Sei: Phila., VIE, 1874; p. 18;/plk vo ne aS Obes 
DUD ie Zea. 22 0p le Vvestionmse 
Pleurobema simulans Stmpson, Syn., 1900, p. 760. 
This species is close to P. patsaligense, but is more elon- 
gated, is darker colored and has a rather higher posterior 
ridge. Some specimens appear almost black. It is much 
shorter than P. strodeanum, and is not black like that species. 
