New LamellibTancMata. — Ulrich. 279 
the beaks, bending down somewhat in front of them. Anter- 
ior end narrow, rather long, equalling one-fifth of tlie entire 
length of the shell; beginning at the junction with the hinge 
line the curve is sharp, then gentle as it merges into the con- 
vex basal line. Posterior end somewhat obliquely truncate ; 
yet curving gently and uniformly from the narrowh' round- 
ed and prolonged postero-basal region into the cardinal mar- 
gin. Umbones full, the obtusely angular umbonal ridge ex- 
tending nearly to the postero-basal margin. Central portion 
of valves transversely flattened. Cardinal slope concave. 
Point of greatest convexity of shell above the center. Surface 
with concentric furrows and fine concentric lines. These are 
crossed by obscure broad radiating lines which probably indi- 
cate former color bands. Both the concentric and radial orna- 
mentation is best develoj^ed in the central portion of the 
valves. 
The shell was very thin, and the anterior muscular impres- 
sion faint. Specimens of this species preserving the shell are 
not likely to be comfounded with any other species known to 
me. Casts of the interior in which the peculiar surface orna- 
mentation would be absent, would not be so readily distin- 
guished from similar casts of several species occuring in the 
Cincinnati rocks. There is however an appreciable difference 
in the outline and in none of these shells, is the umbonal ridge 
so well-marked a feature as in J/", pulchella. 
Position and locality. Rare in the Utica slate horizon of the Cincin- 
nati groujj, at the "river quarries" a little west of Covington, Ky. 
Modiolopsis subtruncata, n. sp. 
Fig. 7. Modiolopsis subtruncata, n. sp. Cincinnati group, Cincinnati, 
Ohio. a. right valve of this species, preserving the shell, b and c end 
and cardinal views of same to show convexity. 
Shell of medium size or smaller, short, a little widest poster- 
iorly, the greatest length and width, respectively, as nine is to 
