GASTEROPODA. 



gitudinal ridges or rows of spines (varices), and the aperture 

 is rounded. 



Fig. 387. — Rostelktria ampla, reduced one-third. Eocene Tertiary. 



In the nearly-related Typhis (fig, 388) there are tubular 

 spines between the varices, and the last of these lodges the 

 posterior siphon. Both Mu- 

 Tcx and Typhis commence 

 in the Eocene Tertiary, and 

 have attained their maxi- 

 mum in existing seas. Tw- 

 phon, like the preceding, 

 ranges from the Cretaceous 

 to the present day ; and 

 Fulgiir (fig. 391, d) is a 

 Tertiary and Eecent form. 



Pisania commences to be 

 represented in the Eocene, 



as do the genera Banella, Triton, and Cancellaria. Fasciolaria 

 and Pyrula (fig. 391, e) commence their existence in the Cre- 

 taceous rocks ; and TmMnella and Trichotropis do not make 

 their appearance till the Miocene. Lastly, the great genus 



Fig. SSS.— Typhis tuMfer. Eocene 

 Tertiary. 



