78 PAL2B0XT0L0GY OF NEW YORK. 



marked by regular, strong, revolving cariniform striae, which are more 

 approximate as they approach the umbilical depression, and all crenulated 

 by concentric striae. 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. Ilamiltonia 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 carinae are 

 developed to nearly equal strength with the others, the resemblance is quite 

 close to some varieties of that species. 



In the usual imperfect and fragmentary condition of specimens, it becomes 

 very difficult to distinguish this form from Cyclonema Hamiltonm. The 

 character of the crenulated revolving carinae 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. Hamiltonm, 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 

 carinae 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. 



