612 UNIO 
Abbeville district, South Carolina; south to northern Flor- 
ida. 
Type localitv, Ogeechee River, Ga. 
Unio pusillus Lea, Pr. Ac. N. Sci. Phila., I, 1840, p. 286; Tx. 
Am: Phil. Soc.; VIII, 1842, p. 220, pl. xvii, he. 46; Obes 
IIT, 1842, p. 58, pl. xvii, fig. 36.—CuHeENu, Ill. Conch., 1858, 
pl. xxxu, figs. 5, 5a, 5>—Kuster, Conch. Cab., 1861, p. 
197, pl. Lx1, figs. 3, 4.—Simpson, Pr. U. S. Nat. Mus., XV, 
1892; pi ALI, plow figs. 26; Syus, tese; a Zes: 
Margaron (Unio) pusillus Laa, Syn., 1852, p. 31; 1870, p. 48. 
Unio buxeus Lea, Tr. Am. Phil. Soc., X, 1852, p. 261, pl. xv, 
he. /13>-Obs., V, 1852. ps 17, ple av, fe. ae 
Margaron (Unio) buxeus Lea, Syn., 1852, p. 29; 1870, p. 46. 
Unio anthony Lea, Pr. Ac. N. Sci. Phila., V, 1861, p. 41; Jl. 
Ac. N. Sci. Phila., V, 1862, p. 197, pl. xxvus, fig. 266; Obs., 
TX, 1863, p. 19; pl. xxvir, fie. 266. 
Margaren (Umo) anthonyi Lra, Syn., 1870, p. 43. 
More inflated and smaller than U. congareus, more elon- 
gated than U. masoni. It is close to U. merus and may be only 
a form of it. In pusillus the greatest degree of inflation is at. 
the posterior ridge and in front of it the shell is somewhat 
wedge-shaped and it is not a very solid species. In merus a 
dorsal view shows the shell to be exactly doubly convex and 
it is rather a solid shell. 
UnIo MERUS Lea. 
Shell small, rhomboid, convex, rather solid, somewhat in- 
equilateral; beaks full, slightly elevated, their sculpture a 
few strong ridges, the lower ones almost doubly looped, the 
upper ones curved sharply up behind; posterior ridge full, 
angled, single, ending behind at the base of the shell; base line 
nearly straight; posterior end decidedly and obliquely trun- 
cated ; surface nearly smooth ; epidermis greenish-yellow, faint- 
ly raved; left valve with two subcompressed pseudocardinals 
and two delicate laterals; right valve with one pseudocardinal: 
