QUADRULA 917 
Unio subtortus SowERBY, Conch. Icon., X VI, 1868, pl. LXxxvu, 
fig. 465.—Herupbr, Conch. Fluv. Nank., VIII, 1883, pl. Lx1, 
fig. 1109. 
Unio retortus Heupr, Conch. Fluv. Nank., VIII, 1883, pl. ivi, 
fig. 100. 
Two examples of this species are before me, one agreeing 
perfectly with Dr. Lea's figure, the other differing a little. In 
one of these the right valve is pushed forward; in the other 
it is pushed back. The line of junction of the valves is curved 
somewhat. It differs from the allied forms in having the disk 
free of nodules and has stronger plications on the posterior 
slope than fibrosa or tientsinensis. 
It is quite probable that when a large amount of material 
can be examined some of the species of this group will have 
to be relegated to the svnonymy. 
QUADRULA TIENTSINENSIS (Crosse and Debeaux ). 
~ 
“Shell almost evenly elliptical, solid, inflated, one valve de- 
cidedly pushed ahead on the other; beaks full and high, sub- 
terminal; surface sculptured with strong, irregular, concen- 
tric ridges and having in the umbonal region a number of tu- 
bercles; epidermis silky, russet or ashy brown, painted with 
bright, green, narrow bands and small blotches ; pseudocardi- 
nals strong, striate and crenulate; laterals with vertical stria- 
tion; beak cavities deep; nacre whitish at the border, yellow- 
ish in the center of the shell. 
Length 65, height 53, diam. 41.5 mm. 
China. 
Unio tientsinensis Crosse and Drpeaux, Jl. de Conch., III, 
1863, p. 257, pl. x, fig. 1—Sowerpy, Conch. Icon., XVI, 
1868, pl. xct, fig. 514, 5340, 5140. 
Margaron (Unio) tientsinensis Les, Syn., 1870, p. 30. 
Quadrula tientsinensis Stimpson, Syn., 1900, p. 708. 
Much more evenly elliptical than tortuosa, the sculpture con- 
sisting of concentric ridges and nodules being very different. 
Q. tortuosa is uniformly colored, while Crosse and Debeaux’ 
species is painted with green, their shell has yellowish nacre 
and that of tortwosa is silvery. 
