S04 
PALEONTOLOGY OF NEW-YORK. 
Surface marked by line close concentric striae, beneath which are dis¬ 
tinct radiating striae, and the latter become more distinct on the 
partially exfoliated surfaces. 
The cast of the ventral valve shows a large rostral cavity, with evi¬ 
dences of strong teeth and extended dental plates. The muscular area is 
narrow and elongate. In the dorsal valve, the muscular imprint reaches 
half way from beak to base of the valve; the septum scarcely reaches 
so far. 
This shell is usually readily distinguished from the other species of the Upper 
Heklerberg and Hamilton groups by its elongate form, which is compressed 
and laterally expanded towards the front; by the remarkable arcuation of 
the ventral valve, and the strong angular lateral ridge which extends from a 
little above the middle to the apex, nearly in the same curve as the junction of 
the valves in their anterior half. 
In this feature, and in the less incurvation of the beak, it is distinguished from 
some varieties of M. nasuta ; and in the same manner it is distinguished from 
M. barrisi and M. haskinsi, which are always proportionally shorter shells. 
The figures 2-7 illustrate the characteristic forms of this species; figures 8-10 show 
the extreme features of the larger individuals. The extreme length is about one inch and 
three-fourths, with a width of a little more than an inch and one-fourth. Figure ll is the dor¬ 
sal valve of a large individual which is much broader than usual in proportion to its length. 
Figure 12 is a cardinal view of a cast of this species, showing the median septum of the 
dorsal valve, and cavities made by the dental lamellae of the ventral valve. 
A single specimen, figure 1, from the Schoharie grit, appears to be of this species. 
Geological formation and localities. This species has been chiefly obtained 
from some loose masses of the upper part of the Corniferous limestone near 
Williamsville, Erie county. One specimen only has been obtained from the Scho¬ 
harie grit, in Schoharie county. 
Meristella barrisi. 
PLATE XLIX. 
Meristella barrisi : Hall, Thirteenth Report on the State Cabinet, p.81. 1860. 
Shell ovoid, more or less elongate and sometimes broadly ovate, gibbous : 
valves subequally convex, sinuate in front. 
Ventral valve gibbous in the middle, the greatest convexity a little 
above the middle of its length, and abruptly sloping to the sides, flat- 
