REPORT OF THE STATE PALEONTOLOGIST 1901 629 



^^as observed. This locality is 5 miles east of the type locality at 

 Portageville, station 14. 



West of the Genesee river the normal Portage fauna, with a 

 few additional species embraces all the fossils found up to the 

 horizon of the sandstones. 



COXCLLSION 



The foregoing statement of facts demonstrates that during 

 the time required for the deposition of 428 feet of upper Gardeau 

 shales and flags, 182 feet of Portage sandstones and 150 feet of 

 •overlying Wiscoy shales in the Genesee river section, the normal 

 Portage fauna continued to hold the ground while in the Naples 

 section at the beginning of this period the succeeding fauna had 

 advanced from the east, established itself and remained, driv- 

 ing out the Portage fauna which never returned. 



The advance of the later invader toward the west was very 

 slow, and probably broken by periods of recession, for in all 

 that time it covered but 25 of the 30 miles between the two 

 sections. 



The upper limit of range of the Portage fauna descends in 

 the strata, very irregularly doubtless, from the top of the Wis- 

 coy shales above Portageville to the bottom of the Grimes sand- 

 stones at Xaples, a vertical decline in the strata of 760 feet in 

 a distance of 30 miles. 



