74 
PALEONTOLOGY OF NEW YORK. 
a very gentle retral curve, abruptly bending backward as they approach 
the peripheral band, crossing which they are continued of nearly or quite 
the same strength as above. The band is simple, limited on each side by 
a slender carination, and marked only by the curving transverse stride. 
The revolving striae below the periphery are often undulating, and in 
some examples stronger than the transverse striae, while the latter are 
usually predominant. 
This species, when preserving the surface-markings, is well characterized 
and readily distinguished from any other form. The spire is more elevated 
than in P. Ella, and the volutions less rounded; the revolving striae are finer, 
and the regular cancellation by the concentric striae gives a textile appearance 
to the surface. 
The substance of the shell is moge delicate than in either of the preceding 
species, except P. delicatula, and all the specimens seen are crushed or other¬ 
wise distorted; the one figured, more nearly preserves the natural propor¬ 
tions. All the smaller specimens observed are flattened from above, as shown 
on plate 28, where the spire scarcely rises above the plane of the outer volu¬ 
tions. A single large specimen, figured on plate 28, is laterally compressed 
so that the true proportions cannot be represented. The diameter of the 
specimens in the collection examined, ranges from three-fourths of an inch to 
about two inches. 
In form and proportions, as well as in the cancellate surface, this species 
may be compared with P. clatlirata of Munster, but differs conspicuously in the 
absence of the elevated band at the summit of each volution. In its surface 
markings this species has much resemblance to the figures of P. turbiniformis, 
Meek & Worthen, from the Coal measures of Illinois; but the New York 
species has a less elevated spire, greater proportional width and ventricose 
volutions. 
Formation and localities. This species occurs in fine shales of the Hamilton 
group at Bellona, in Yates county, N. Y., and at Monteith’s Point on Canan¬ 
daigua lake. A single specimen, apparently a cast of this species, has been 
found at Fultonliam in Schoharie county, N. Y. 
