THE HAMILTON IN OHIO 591 
other words, a great period of sea encroachment had set in which 
affected maialy the northwestern coast of Appalachia and the land 
area beyond the Indiana basin. Ohio therefore lay beneath the 
same sea, much enlarged since the earlier Devonian, as that covering 
the southern portion of New York in Hamilton time, and naturally 
contains deposits contemporaneous with those of New York. 
As at present defined, the Devonian system in Ohio comprises 
the following formations:' 
c) Cleveland shale 
4. Ohio shale { 6) Chagrin formation 
a) Huron shale 
. Olentangy shale 
2. Delaware limestone 
t. Columbus limestone 
Ww 
The Columbus limestone is the southern extension of the Dundee 
of Michigan and the eastern extension of the Jeffersonville of Indiana 
and Kentucky. This equivalence is shown, not only by lithological 
similarity and stratigraphic identity, but conclusively by the faunal 
unity. These Indiana, Michigan, and Ohio limestones are but the 
local representatives of the Onondaga of New York, or, if we accept 
the conclusion of Ulrich and Schuchert,? which is also supported by 
Dr. J. M. Clarke,’ that the Onondaga fauna invaded the state from 
the west, perhaps it is better to say that the Onondaga limestone is 
but the New York representative of these limestones. 
But what of the Delaware limestone? Newberry and Orton 
included it with the Columbus as the Ohio equivalent of the “ Corni- 
ferous” (Onondaga).4 This, however, seems to have resulted 
mainly from a mistaken correlation of the deposits occurring in the 
eastern part of Sandusky,’ where the upper layers of the Columbus 
limestone show some variation, both lithological and faunal, from 
that of the vicinity of the city of Columbus,.and approach somewhat 
the appearance of the true Delaware. Professor Winchell, however, 
t Prosser, Report of the Geological Survey of Ohio, Fourth Series, Bulletin No. 7, p. 3. 
2 Loc. cit., pp. 652, 653, 663. 
3 [bid.,; pp. 667, 668. 
4 Report of the Geological Survey of Ohio, Vol. I, Part 1, pp. 144, 150, 151; Vol. II, 
Part 1, pp. 190-92, also 290, 3d note; Vol. III, p. 606. 
5 Prosser, Journal of Geology, Vol. XIII, No. 5 (1905), pp. 439-42. 
