212 NEW YORK STATE MUSEUM 



Diaphorostoma niagarense Hall (Fig. 141) (1852. Pal. N. Y. 

 2:287, pi. 60) 



Distinguishing characters. Globose contour; three to four volu- 

 tions; large body whorl, inflated toward the dilated aperture; deeply 

 depressed sutures; fine longitudinal and strong transverse striae. 

 Not infrequently a sinuosity is indicated by the lines of growth. 



<C 



V 



Fig. 141 Diaphorostoma niagarense 



Found in the Clinton limestone lenses, and the lower and middle, 

 and rarely the upper Rochester shale at Niagara. Also at Lock- 

 port and elsewhere (Hall). 



Genus pleurotomaria De France 



[Ety. : -Xeupd, side; ro/j.rj, sl cut] 



(1824. Tableau d. corps organises fossiles, p. 114, and Diet. sci. 



nat. 41 1381 ) 



Shell Trochus -shaped, more or less conic, with or without 

 umbilicus; volutions angular, flattened, or rounded, their surfaces 

 variously ornamented; aperture subquadrate to suborbicular, the 

 inner lip thin. The outer lip bears a narrow, deep fissure or sinus, 

 which is the unclosed continuation of a revolving band. 



Pleurotomaria littorea Hall (Fig. 142) (1852. Pal. N. Y. 2:12, 



pi. 4 (bis)) 



Distinguishing characters. Me- 

 dium size; subconical form; 

 three to four somewhat ob- 

 tusely angular volutions, which 



Fig. 142 Pleurotomaria littorea 



enlarge rapidly; small umbilicus. 

 Found in the upper Medina sandstone at Lockport (Hall). Frag- 

 ments in the same rock at Niagara seem to be of this species. 



