794 PLEUROBEMA 
Unio pyrifornus Lea; Pro Ac Nasc: Phila x 1857 ps a 
Jl, Ac. N.seis PhilagelV ses erp ‘Copii che 50.5 Ose 
VI, p60; pl xi, figss5o. 
Margaron (Unc) pyriformis Lea, Syn., 1870, p. 40. 
Pleurobema pyriformis SIMPSON, Syn., 1900, p. 762. 
Close to P. argenteum, but smaller, more nearly elliptical, 
with a brighter epidermis and salmon nacre. 
PLEUROBEMA AMABILE (Lea). 
Shell rather small, subovate, convex, solid, inequilateral ; an- 
terior end rounded, base curved; posterior slope obliquely sub- 
truncate; posterior ridge high, narrowly rounded, ending be- 
hind in a point just below the median line; beaks high and 
full, their sculpture a series of strong ridges, running nearly 
parallel with the growth lines, but heavier and suddenly turn- 
ed up behind; epidermis almost smooth, tawny or tawny- 
brownish, subshining, sometimes very feebly rayed; left valve 
with two solid, subcompressed, rough pseudocardinals and two 
short laterals; right valve with one pseudocardinal and a ves- 
tigial tooth in front of and behind it, and one somewhat dou- 
ble lateral ; beak cavities shallow but compressed ; muscle scars 
small; nacre whitish or straw-colored, iridescent and thinner 
behind. 
Length 37, height 25, diam. 16 mm. 
Type localitv, Butler, Taylor County, Georgia. 
Unio amabilis Lea, Pr. Ac. N. Sci. Phila., IX, 1865, p. 89; Jl. 
Ac Ne Sem Phila, Vil, 1869). p:-257, pixxx te) 72 Ops 
XII, 1869, p. 17, pl. xxx, fig. 72.—SIMPSON, Syn., 1900, p. 
720. 
Margaron (Unio) amabilis Lea, Syn., 1870, p. 37. 
Apparently close to the Unio pyriformis of Lea and it may 
connect with that species. Judging from the type, it is short- 
er, smoother and lighter colored than that species and has a 
somewhat higher posterior ridge. 
PLEUROPEMA MCDICUM (Lea). 
Shell small, subrhomboid, inequilateral, convex to subinflat- 
ed, subsolid : beaks full and high, sculptured with a few strong 
ridges ; posterior ridge rather full, but not distinctly biangulate, 
