UNIO 643 
Unio Fuscatus Lea. 
Shell long elliptical or slightly obovate, compressed or sub- 
compressed, rather thin; beaks low, somewhat compressed, 
their sculpture consisting of subconcentric, subnodulous 
ridges; posterior ridge !ow, usually more or less double, end- 
ing behind at and below the median line in a feeble biangula- 
tion; surface nearly smooth; epidermis pale reddish-brown or 
ashy-brown, often feebly rayed with green, shining in the 
young shells, showing lamellz in the later growth and often 
covered behind with hair-like conferve; left valve with two 
small, ragged pseudocardinals and two delicate, curved lat- 
erals; right valve with two pseudocardinals, the upper small, 
and one lateral; beak cavities shallow; muscle scars scarcely 
impressed ; nacre coppery or purplish. 
Length 67, height 36, diam. 18 mm. 
I,ength of type, 44. height 22, diam. 12 mm. 
Length 45, height 27, diam. 14 mm. 
Florida. 
Type locality, Black Creek, Fla. 
Unio fuscatus Lea, Desc. 12 Uniones, 1843, (no pagination). 
tei. mil SOC, 1X, Tots? p. 277, pl. xt, fie: 4; Obs: 
IV, 1848, p. 35, pl. x1, fig. 4.-—Kuster, Conch. Cab. Unio, 
1848, p. 203, pl. Lxvii, fig. 2—Rereve, Conch. Icon., XVI, 
1865, pl. xx1, fig. 95.—Simpson, Pr. U. S. Nat. Mus:, XVI, 
IeO2i ps 420; pls LX, fSS..2. 45" Syil., 1900, p..717: 
Margaron (Unio) fuscatus LEA, Syn., 1852, p. 30; 1870, p. 48. 
Young shells of this species are very close to U. occultus 
and certain specimens of U. tortivuws, but are generally a little 
more delicate than either. The older shells are thinner and have 
a peculiar texture and a coppery tint not seen in either of the 
above-mentioned forms. The old shells often become some- 
what rhomboid, widening out at the posterior end, and the 
epidermis is roughened on account of being pinched up into 
delicate lamellz. Old shells often have a considerable growth 
of hair-like conferve at the posterior end. I have a dwarf, 
stunted form before me from Juniper Creek, Lake George, 
Flerida, which is much narrowed in front. 
