1560 NEW YORK STATE MUSEUM 
Many interfingerings®® of these phases naturally occur, but on the 
whole these faunal and lithic zones shift progressively westward 
giving a westerly overlap. The “ Portake-Chemung-Catskill ”’ suc- 
cession is thus a homotaxial one, assuming different time values on 
every meridian and of steadily later date as to the lower and upper 
“Chemung” limits in going westward. The relations are best 
grasped by aid of the following diagram : 
It will be seen that this is merely carrying toward conclusion the 
concepts advanced years ago®® by Dr John M. Clarke. 
The tracing of the beds is complicated by low and sometimes 
irregular anticlinals, whose unraveling will eventually be of import 
in locating supplies of oil and gas. 
“UW, Su Geol Sary. IBitil, Bi, p. Ad=27. 
