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PALAEONTOLOGY OF NEW YORK. 
Modiomorpha recta, n. sp. 
PLATE XXXV, FIG. 9. 
Shell of medium size, sub-ovate; length less than twice the height; basal 
margin nearly straight, or gently convex, curving abruptly at the anterior 
and posterior extremities. Posterior end somewhat abruptly rounded. Car¬ 
dinal margin nearly straight. Anterior end short, abruptly rounded at the 
extremity ; indistinctly limited by a broad flattening of the valves extending 
from the umbo to the base of the shell, about one-third the length from the 
anterior end. 
Valves very convex, gibbous on the middle and umbonal regions, somewhat 
abruptly declining toward the anterior and posterior extremities; depth less 
than one-half the length of the shell. 
Hinge-line straight, slightly oblique, a little less than half the length of 
the shell. 
Beaks sub-anterior, small, closely appressed. Umbonal region gibbous to 
about the posterior third, thence regularly declining to the margin. 
Test of moderate thickness, concentrically striated. 
Anterior muscular impression strong, with an accessory muscular pit. Pal- 
lial line not deeply impressed, following the general course of the basal 
margin, recurving at the posterior extremity, and terminating in a broad 
posterior muscular impression. The space between the pallial line and um¬ 
bonal region is marked by pitted vascular lines. 
One of the specimens described has a length of 57 mm., height 32 mm., 
and depth of both valves 25 mm. Another specimen measures 52 mm. 
in length and 30 mm. in height. 
The general form of the shell is similar to M. subalata, but it has not the 
distinct umbonal ridge, nor alate post-cardinal slope. 
Formations and localities. In the cherty-layers of the Hamilton group, in 
Clarke county, Ind.; and in the Corniferous limestone of Canada West. 
