142 PALAEONTOLOGY OF OHIO. 



tion forming nearly two-thirds of the entire length of the shell. Aper- 

 ture elongate, narrow, acutely pointed above and broad below, forming 

 more than one-half of the length of the body volution. Suture faintly 

 marked and close. Surface apparently smooth. 



The species differs from S. ventricosa, Hall, from the Onondaga salt 

 group of New York, and also from the Niagara formations of Wisconsin, 

 in being much more slender in proportion to its length, as well as being 

 a much longer shell; also, in having the spire erect instead of bent to 

 one side, as in that species, and in having the volutions more rapidly in- 

 creasing in length. From S. elongatus, Conr., of the Trenton limestone, 

 it differs in being proportionally shorter in the spire as compared with 

 the body volution, and not so regularly tapering, the whole being round- 

 ed toward the apex. It is, however, so closely related in form to that 

 species that it is exceedingly difficult to draw a very satisfactory com- 

 parison. This species is the first one noticed in rocks of this age in this 

 country, so far as we are aware, that has not the spire bent on one side 

 like that of S. ventricosa. 



Formation and locality: In the limestones .of the Niagara group (upp'er part, or 

 Guelph horizon), at Clifton, Greene county, Ohio. State collection. Collected by 

 Prof. E. Orton. 



Genus PLEUROTOMAKIA, DeF ranee. 

 Pleurotomaria occidens. 



Plate 8, fig. 2. 



Pleurotomaria occidens, Hall ; 20th Rept. State Cab., pp. 342 and 364, pi. 15, figs. 11, 12 ; 

 2d Ed., p. 392, pi. 15, figs. 11, 12, and pi. 25, figs. 9, 10. 



Shell rather large, depressed; consisting of from two to three rapidly 

 enlarging volutions. Spire low, not equaling one-half the height of the 

 shell. Volutions flattened on the upper side; strongly carinate and 

 banded on the periphery, and regularly rounded below, except near the 

 aperture of the finished shell, where it becomes prolonged or extended 

 downward in the middle. Umbilical region broadly impressed, but not 

 perforate, the surrounding surface gradually rounding into the cavity. 

 Columellar lip thickened, forming a callous over the umbilicus : reflected 

 and curved in the lower part. Aperture large, sub-triangular, somewhat 

 transverse in the specimen ; prolonged and pointed in the lower lateral 

 portion. 



Surface of the shell marked on the upper surface of the volutions by 



