NIAGARA FALLS AND VICINITY 



217 



Gomphoceras ? sp. (Hall. 1852. Pal. N. Y. 2:290, pi. 61) 



Distinguishing characters. Subfusiform aperture narrowed, grad- 

 ually tapering to the extremity; surface striated transversely. 



This fossil has the general form and appearance of Gompho- 

 ceras, though I am unable to discover any marks of septa. The 

 greatest expansion appears to be at about one third of the distance 

 from the aperture to the apex. 



Found " in a fragment of limestone below the cliff at Niagara 

 Falls " (Hall). 



Fig. 149 Trochoceras gebhardi, two thirds natural size 



Genus trochoceras Hall 



[Ety. : rpoxo?, a wheel; -/Jpa?, a horn (named from its trochus 

 or top-like shape)] 



(1852. Pal. N. Y. 2 :335) 



Shells turbinate or trochiform; spire elevated as in Gastropoda, 

 more or less ventricose and umbilicated; aperture rounded or round 

 oval; volutions above the outer one with septa; siphuncle sub- 

 marginal or dorsal. 



Trochoceras gebhardi Hall (Fig. 149) (1852. Pal. N. Y. 2:335, 

 pl- 77> 77^'^ Grabau. Geol. soc. Am. Bui. 11:371, pi. 21) 



Distinguishing characters. Deep and wide umbilicus with angular 

 margins; cross-section of body whorl irregularly subhemispheric; 



