610 UNIO 
Streams from the Congaree River, South Carolina, south 
to northern Florida. 
Type locality, Savannah River, Ga. 
Unio forbesianus Lea, Pro Amt Phil Soc, V7, 1552... 255. 
Ee Aan Phily Soci, Xe 18525 ps 204, pli xvi tie 175. Ose 
1852, p. 20, pl. xvi, fig. 17—Kuster, Conch. Cab. . Unio, 
1861. p. 310, pl. Lxrx, fig. 6—Musecrave, Phot. Conch., 
1863, pl: 11, fig. 2—SOwERBY eats leon, XVI; 1868: pk 
LXXI, fig. 361.—SIMPSON, Pr. USs:eNat Mus., XV 192; 
DAATO; Pls. XLIX) Nos 3 uy hese2ese st {QO00}p- 70%: 
Margaron (Unio) forbesianus LEA, Syn., 1852, p. 24; 1870, p. 
37: 
Unio moussonianus Lea, Tr. Am. Phil. Soc., X, 1852, p. 268, 
pl. xvilighic. 223+ Obse Vs, 1852, ps 24, ple va leek 22. 
Margaron (Unio) moussonianus tee SYN. 1852, p. 20,1870; 
p. 46. 
Ume corvus Lea, Pr. Ac. N. Sci. Phila., T1, 1859; p. 1125, Jl. 
Acad. N. Set. Philas, 1Vs1850;pe2r7% al SVIL, fs. O75 Obs., 
VII, 1850, p. 35, pl. xxvit, fig. 97—Sowersy, Conch. Icon., 
JX VAGSI868 pl, Tacx yi ie ie 
Margaron (Unio) corvus Lea, 1870, p. 37. 
Unio vestitus Lua, Pr. Ac. N. Sci. Phila., V, 1861, p. 393; JI. 
Ac. N: Sen Phila; V,91862;\p; 180 pl=xxv, fie 250 - Obs. 
LX¢a8624p. Ti, pl: xxvcnss 250: 
Margaron (Unio) vestitus Lea, Syn., 1870, p. 50. 
It is difficult to draw up any description, which will prop- 
erly cover and yet separate from other forms this and most 
of the allied species of the crassidens group of Unios. Ina 
general way the shells of this species are thinner and smoother 
than those of incrassatus and have deeper beak cavities, but 
many intermediates are found. which more or less connect not 
only these two, but this with other so-called species. Indeed 
the group is one of the most difficult to treat of American 
Unios. U. moussonianus, U. corvus and U. westitus of Lea 
do not seem to me to possess any claims to distinction. 
