UNIO 647 
state, dark brown or black when old, subshining ; pseudocar- 
dinals small, rough, stumpy; laterals short, remote; muscle 
scars small, well marked ; nacre silvery, white, salmon, copper- 
color or purplish, iridescent behind. 
Length 56, height 30, diam. 18 mm. 
Length 43, height 24, diam. 14 mm. 
length 39, height 21, diam. 12 mm. 
Chattahoochee Kiver system; south into Florida. 
Type locality, Chattahoochee River, Columbus, Ga. 
Unio nigellus Lea, Pr. Am. Phil. Soc., V, 1852, p. 251; Tr. 
Am Phil Soc: Xs 1852; .p4 263) plo xxiv, fig. 42> Obs. V, 
1852, p. 39, pl. xxiv, fig. 42—SIMPSON, Syn., 1900, p. 718. 
Margaron (Unio) mgellus LEA, Syn., 1852, p. 30; 1870, p. 53. 
Unio demgratus Lea, Pr. Ac. N. Sci..Phila., 1X, 1857, p. 171; 
Jl. Ac. N. Sci. Phila., IV, 1859, p. 200, pl. xx111, fig. 83 ; Obs., 
VII, 1859, p. 18, pl. xx, fig. 83.—Simpson, Pr. U. 8. Nat. 
Mus., XV, 1892, p.\422, pl. Lxv, figs1. 
Margaren (Unio) denigratus LEA, Syn., 1870, p. 52. 
Distinguished from related species by being considerably 
higher behind than in front, by having the greatest diameter 
at the posterior ridge and by its soft, rich nacre. 
Unio pPiner B. H. Wright. 
Shell long rhomboid, subinflated, subsolid, inequilateral ; 
beaks apparently not very high or full, their sculpture not 
seen; posterior ridge full, angled, narrowly double, ending be- 
hind in a feeble biangulation at or near the base of the shell ; 
dorsal and ventral lines nearly straight and parallel; dorsal 
slope obliquely truncated above; anterior end rounded and 
slightly angled above; surface nearly smooth; epidermis with 
delicate lamella, but shining, reddish-brown, tawny and green, 
faintly rayed in fine specimens; pseudocardinals subcom- 
pressed, ragged; laterals nearly straight; muscle scars shal- 
low ; nacre white, purple, brown or copper-colored, rather rich 
and bright: iridescent behind. 
Length 66, height 31. diam. 20 mm. 
North Florida. 
Type locality, Lake, Hernando Co., Fla. 
