378 
PALAEONTOLOGY OF NEW YORK. 
Valves moderately convex, below and posteriorly, becoming gibbous above 
the middle. 
Beaks sub-anterior, prominent, closely incurved and rising above the 
hinge-line. Umbonal slope rounded, prominent near the beaks, but grad¬ 
ually merging into the general convexity about the middle of the length 
of the shell.' There is a distinct cincture extending a little backward from 
the beaks to the basal margin. 
Surface marked by fine concentric striae, and extremely fine, pustulose, 
radiating striae; also by strong concentric undulations, which are sometimes 
duplicate or intercalate near the anterior end and rarely in the middle of 
their length, becoming obsolete before reaching, or upon, the post-cardinal 
slope. The undulations are often a little deflected on the line of the cincture. 
Ligamental area distinct and elongate. Characters of the interior unknown. 
One specimen has a length of 40 mm. and a height from beak to base of 22 
mm. A smaller individual has a length of 20 mm. and a height of 13 mm. 
This species is easily distinguished from any in the Hamilton group by the 
strong, nearly vertical, mesial cincture and elongate form. 
The cincture in G. subarcuata is much farther anterior than in this species. 
From G. communis it is distinguished by the greater distance of the beaks 
from the anterior end; by its narrower posterior extremity, and by the more 
nearly vertical direction of the mesial cincture. 
Formation and localities. In the arenaceous beds of the Hamilton group, near 
Fultonham, and other parts of Schoharie county, and in the soft shales of the 
formation on the shores of Seneca and Canandaigua lakes, N. Y. 
Grammysia communis, n. sp. 
PLATE LXI, FIGS. 24-28 ; AND PLATE XCIII, FIG. 20. 
In part Grammysia Hannibalensis, (Shumard), Hall. Prelim. Notice Lamellibranchiata, 2, p. 62. 1870. 
“ Grammysia (Leptodomus?) Hannibalensis, Hall. Pal. N. Y., vol. v, pt. 1. Plates and Explana¬ 
tions: PI. 61, figs. 23-33. 1883. 
Not Allorisma Hannibalensis, Shumard. Geol. Surv. Missouri, Rep., pt. ii, p. 206, pi. c, fig 19. 1855. 
Shell small, ovate-cuneate; length less than twice the height; basal margin 
gently curving with a slight constriction just anterior to the middle of the 
