44 FIFTEENTH REPORT ON THE CABINET OF NAT. HISTORY. 



" rectilinear towards the labrum, slightly convex above the aper- 

 " ture." 



Until the present time, I have failed to recognize in our limestones any 

 species of Pleurotomaria that could be identified with the P. U7iisulcata 

 of Conrad. I have now before me an imperfect specimen which has the 

 form and proportions of spire and body-whorl, with a strongly banded 

 suture, represented in the figure of P. unisulcata. The apex is imperfect, 

 and the upper side of the body-volution a little more flattened ; the aper- 

 ture also is imperfect, but has the form given in the figure of Conrad. 

 Some portions of the shell show concentric and revolving striae ; but the 

 back of the outer volution is too imperfect to show any spiral band, though 

 the bending of the striai indicates a sinuosity in the dorsal angle of the 

 peristome. 



Geological formation and locality. In Upper Helderberg limestone at 

 Schoharie. 



PLEUROTOMARIA LINE ATA. T^ ^ / ^ 



Turbo lineata : Hall, Geol. Report 4th District New-York, 1843, p. 193, f. 1. 



Shell turbinate. Spire ascending, higher than wide. Volutions four 

 or five, regularly and evenly convex, gradually expanding to the 

 body-whorl which is ventricose, rounded below and concave in 

 tjie middle : umbilicus small or none. Aperture round. mm 



Surface marked by equal regular revolving strige on the upper and 

 lower sides of the volutions, which are crossed by fine concentric 

 striae : these, on the periphery, are bent abruptly backwards along 

 a broader space than is usual between two revolving striae, and 

 sometimes there is a distinct band upon the periphery. 



This species varies in form and proportions, from compression and acci- 

 dent, so that some specimens are proportionally much more elevated than 

 others. In the soft calcareous shales of the Hamilton group, this fossil 

 usually occurs in the form of casts, and it is not unfrequently covered by 

 encrusting coral or brj^ozoa. In its greatest height, the shell reaches nearly 

 an inch. A very symmetrical specimen measures about seven-eighths of an 

 inch in height, with an equal breadth. 



Geological formation and locality. In the calcareous shales of the Ha- 

 milton group ; Seneca and Cayuga lakes. 



[ August, 



