948 CUNEOPSIS 
while in both the species of Arconaia they are remarkably 
shallow: in fact they have no beak cavities at all. The elon- 
gation of the shells of these forms, their dark, silky, unicol- 
ored epidermis, the oblique, elongated posterior muscle scars 
and the hint at a pallial sinus in some of them and the tortion 
of the shell are characters common to Arconaia. In this spe- 
cies the nacre outside the pallial line is decidedly granularly 
radiate striate and there are indications of the peculiar nacre- 
ous calluses behind the laterals, characters seen to some ex- 
tent in other species of the group, in some specimens of Ar- 
conaia and many of the forms I have placed in Quadrula. 
CUNEOPSIS RUFESCENS .(Heude). 
Shell long rhombic, subsolid, inflated, inequilateral; beaks 
full and high; posterior ridge well developed, narrowly round- 
ed, ending in a point near the base of the shell; above it there 
is a shallow, radial depression; anterior end rounded; basal 
and dorsal lines nearly straight and subparallel; posterior end 
obliquely truncated above; surface nearly smooth, covered 
with a greenish-brown, silky epidermis; left valve with two 
high, compressed pseudocardinals, which are partly united, the 
hinder being slightly triangular, with a deep pit below and 
between them; left valve with one pseudocardinal; laterals 
two in the left valve and one in the right ; anterior scarsdeep ; 
posterior scars shallow, slightly oblique; beak cavities deep ; 
nacre warm flesh-color, lighter colored at the edge, thinner and 
iridescent behind; pallial line with a shallow sinus behind. 
Length 70, height 28, diam. 24 mm. 
Province of Kiang-Si, China. 
Unio rufescens Heupr, Jl. de Conch., XXII, 1874, p. 113; 
Conch. Fluv. Nank., I, 1875, pla, fig. 2: 
Cuneopsis rufescens Simpson, Syn., 1900, p. 805. 
The beak sculpture is partly visible in one of the valves of 
a specimen in the National Museum collection and the poste- 
rior part of it consists of fine, radiating lirze, such as is seen 
in some of the North American Uniones. This species may 
at once be distinguished from the other members of the group 
by its obliquely and decidedly truncate posterior end. 
