PILEUROBEMA 793 
dull, dirty tawny with a tint of green, showing faint rest 
marks; pseudocardinals triangular, nearly smooth, two in the 
left valve and one in the right; laterals two in the left valve 
and a double one in the right: muscle scars shallow ; beak ecav- 
ities not impressed; nacre pale dirty violet, thinner behind. 
Length 40, height 28, diam. 16 mm. 
Type locality, Stump Creek, northwest Georgia. 
Unio georgianus Lita, i, Aim. Phil s0¢. "bE tear, py ar 5s. 
Am. Phil. Soc., VIII, 22). 235, pl. xx. hie. 4g Obs. TIT. 
1542. Pp. AZ. pl -XXE, ee 49.—CHENU, Ill. Conch., 1858, pl. 
ARE, WIS, 3, 3a). 30: 
Margaron (Unio) georgianus Lea, Syn., 1852, p. 27; 1870, 
p. 42. 
Pleurobema georgiana SIMPSON, Syn., 1900, p. 761. 
I am uncertain as to the position of this species. I have 
seen only the type, which is broken and in rather bad condi- 
tion. It is a remarkably lenticular form, with a dull, dirty 
brownish or greenish-tawny epidermis. 
PLEUROBEMA PYRIFORME (Lea) 
Shell subelliptical or subrhomboid, subcompressed, solid, in- 
equilateral; beaks apparently neither full nor high; posterior 
ridge narrowly double, ending above the base line in a bian- 
gulation: anterior end rounded; basal and dorsal outlines 
curved, the former least so; the outline of the dorsal slope is 
sometimes elevated almost into an angle at or behind the liga- 
ment; surface finely, concentrically striate; epidermis tawny 
or tawny-brown, often shaded or clouded with green; more or 
less shining, polished at the umbonal region; hinge rather 
strong ; pseudocardinals two in the left valve and one to three 
in the right; laterals two in the left valve and one in the 
right: beak cavities shallow; muscle scars small, not deep: 
nacre salmon, thinner behind. 
Length 54, height 33, diam. 17 mm. 
Length 52, height 29, diam. 16 mm. 
Type locality, near Columbus, Georgia. 
