No. 136.] 105 



suture in the first volutions, and a littje above the obtuse angle 

 on the last volution. 



This species, occurring with the preceding, is readily known by its 

 shorter spire and obtuse angularity of the last volution. 



Geological formation and locality. Upper Helderberg limestone, Ohio. 



PLEUROTOMARIA KEARlfYI (n.s.). 



Shell large, trochiform. Spire short, consisting of three or four 

 volutions, which rapidly increase in size from the apex : upper 

 volutions depressed-convex on the sides ; the suture somewhat 

 canaliculate, and carinate above by the base of the volution ; 

 the last volution flattened on the upper third, prominent above 

 the middle and flattened on the lower half, marked just above 

 the base by a strong simple angular carina : lower side of the 

 volution prominent in the middle, depressed towards the 

 umbilicus; aperture transverse, somewhat semioval. Surface 

 marked by strong unequal strias, which bend slightly back- 

 wards from the suture, and, in passing the upper more promi- 

 nent part of the volution, curve a little forward, but do not 

 become vertical ; bending abruptly forward on the carina, 

 again curve a little forward, and then backward into the um- 

 bilicus. 



This shell reaches the dimensions of more than two inches in height 

 by three inches in diameter on the base, while some individuals are four 

 inches across the base. 



Geological formaiion. Upper Helderberg limestone. 



PLEUROTOMARIA HEBE (n.s.). 



Shell conical, hemispheric, rounded upon the lower side ; the 

 volutions above flattened, and nearly in the same plane from 

 the apex to the outer edge of the last volution; the spire 

 above the aperture about equal to the height of the aperttire. 

 Volutions about four, very gradually expanding to the last 

 one, which is ventricose and angular on the outer margin ; 

 [Assembly, No. 136.] 14 



