34 The American Geologist. 
July 1903. 
The bed of shale at Prout's Station presents no difficulty, 
as it lies just on the horizon where the Hamilton would be ex- 
pected. But the occurrence of Spirifera mucronata (pennata) 
in the limestone, as Dr. Newberry admits, although nearly at 
its top, is a presentation of Hamilton affinity that cannot be 
overlooked. I make no reference here to professor Winchell's 
Olentangy shale, because it has no bearing upon the question, 
but has been brought into the discussion by a confusion on the 
part of some of the writers on the subject. 
An important advance was made in the study of the Lower 
Devonian rocks of Ohio when, in 1878, a Marcellus horizon 
was recognized near Columbus by professor Whitfield. His 
paper on the subject appeared in 1882 in the form of advance 
sheets of the seventh volume of the "Geology of Ohio." 
The following section of the strata in question is given by 
professor Orton : — 
No. 4. Fifteen feet of bluish, somewhat marly shale, the Olentangy 
shales of N. H. Winchell. This is followed above by the Huron shales, 
the supposed equivalents of the Genessee shales and Portage shales of 
New York. 
No. 3. Thirty feet of thin-bedded shaly limestone, the Delaware 
beds of Prof. Orton; the upper part of this is supposed to represent the 
beds of similar character at Delaware, O., which contain the large fish 
remains. 
No. 2. A thin layer of limestone, four to six inches thick, densely 
filled with teeth, plates and bones of fishes, locally known as the Bone- 
bed. 
No. 1. A heavy bedded limestone about thirty feet thick, represent- 
ing the Columbus quarries, including the coral beds and those contain- 
ing the large cephalopods. 
The shale mentioned above (No. 3) with its characteristic 
fossils, I have no hesitation in pronouncing the equivalent of 
the Marcellus shale of New York. It lies only a few feet 
above the Bone-bed. Admitting this, the rocks above this limit 
should represent the Hamilton group of New York. 
But, on a close examination of the fossils, professor Whit- 
field was unable to draw any very clear line of separation, even 
at the Bone-bed, the number of species yet known not to pass 
below it being, he says, very few, while numerous species 
abounding in the Corniferous of New York are found both 
above and below it. 
Full consideration of all the statements referred to leads 
to the conclusion that the planes of division between these 
