596 CLINTON R. STAUFFER 
the few remaining ‘‘Corniferous”’ species were better able to 
survive. 
Gathering all of the available evidence, there seems to be no sub- 
stantial support for any other conclusion than that the base of the 
Delaware marks the beginning of the Hamilton period in Ohio. 
Whether the Olentangy shale also belongs to the Hamilton or 
Erian period, or how much of the deposits above the Delaware lime- 
stone belong to that age, is beyond the intentions of this paper. There 
are some reasons for believing that this shale should rather be classed 
with the succeeding formation, since other bands of a very similar 
if not identical, lithological nature occur within what is considered 
the Ohio shale. It seems certain, however, that Dr. Newberry’s Prout 
Station section is Hamilton.t If this be the northern equivalent of 
the Olentangy shale, as is very generally supposed, there can be no 
further question as to its age, and the total thickness of the Hamilton 
in central Ohio is then at least 60 feet. 
In the northwestern part of the state the Olentangy shale is appar- 
ently wanting, so that the limestones and shales (Traverse) succeed- 
ing the Columbus limestone probably represent both the Delaware 
limestone and the Olentangy shale in that section. ‘The relations 
existing between these deposits in Ohio, Michigan, and New York 
may then be stated somewhat as follows: 
Michigan Ohio New York 
T Olentangy shale Hamilton beds 
sae One Delaware limestone Marcellus shale 
Dundee limestone Columbus limestone Onondaga limestone 
t Report of the Geological Survey of Ohio, Vol. II, Part I, p. 188. 
