78 
PALAEONTOLOGY OF NEW YORK. 
marked by regular, strong, revolving cariniform strise, which are more 
approximate as the}^ approach the umbilical depression, and all crenulated 
by concentric strise. Peripheral band narrow and prominent, margins 
carinate, and the intermediate space marked only by curving striae. 
Above and below the band, there is usually a broader smooth space than 
between the cariniform striae. 
In some specimens the transverse striae are conspicuous only in crossing the 
revolving striae, while in others they are conspicuous and dominate the 
revolving striae. In nearly all the specimens there is a distinct alternation 
in the strength of the revolving lines, and the finer ones become sometimes 
obsolete. 
A critical comparison with the figure given by Mr. Conrad leaves some 
doubt whether the proper identification has been made; and since no¬ 
peripheral band is mentioned in the description or represented in the figure, 
it is possible that the fossil described is a species of Cyclonema, of the form of 
C. Jlarniltonm or C. multilira. See illustrations on plate 12. 
The species here indicated never has the revolving striae equal. It 
approaches, in its general aspect, P. Itys , but the volutions are not so rounded 
on the upper side; in some examples, where the subordinate carinse are 
developed to nearly equal strength with the others, the resemblance is quite 
close to some varieties of that species. 
In the usu'al imperfect and fragmentary condition of specimens, it becomes 
very difficult to distinguish this form from Cyclonema Hamiltonice. The 
character of the crenulated revolving carinse is very similar, and, in the 
absence of the peripheral band, the only distinguishing feature observed is 
the wider space below the suture, in C. Hamiltonice , which is free from revolving 
lines, and marked only by finer concentric striae,—a condition not character¬ 
istic of this species of Pleurotomaria. 
It is distinguished from the following species by its numerous revolving 
carinse and the simple bicarinate peripheral band. 
Formation and localities. In the shales of the Hamilton group, at Fultonham, 
Schoharie county, and on the shores of Cayuga and Canandaigua lakes, N. Y. 
