592 CLINTON R. STAUFFER 
having made an extensive study of these outcrops over the state, 
pronounced them of Hamilton age.t| Dr. Newberry agreed that the 
Olentangy shale, or at least the deposit immediately overlying his 
‘“Corniferous” in the northern part of this state, may be Hamilton,? 
and this was evidently supported by the fauna of the Prout limestone, 
a thin fossiliferous layer occurring immediately below the Huron shale 
in northern Ohio, but he strenuously objected to the correlation of 
the Delaware with the Hamilton of the east.3 
Some time later (1878) Dr. Whitfield visited central Ohio and 
discovered the brown shale carrying a Marcellus fauna at the base 
of the Delaware. This, he says, forms ‘‘a dividing line between 
the lower and upper Devonian, as between the limestones of the Upper 
Helderberg and those that properly refer to the Hamilton period.’’4 
Again referring to Ulrich, Schuchert, and Clark, we find that the 
Marcellus shale fauna very likely entered southeastern New York 
from the Atlantic, and thence spread westward. Deposits of unques- 
tioned Onondaga in western New York are in all probability contem- 
poraneous with true Marcellus deposits in the eastern part of the 
same state.° This may also be true of the upper part of the Colum- 
bus limestone, but the finding of Marcellus deposits in this vicinity 
(Columbus), even though meager, proves that “‘the invasion of the 
black muds which produced the Marcellus beds, and with these the 
diminutive fauna characteristic of these beds,” reached as far west 
as central Ohio, and hence marks an epoch of change which cannot 
easily be overlooked. By the time this Marcellus invasion had. 
reached the eastern shore of the Cincinnati island its impetus seems 
ty have been nearly exhausted, as the brown, shaly portion of the 
Delaware measures but 6 feet and does not occur at all in Indiana, 
nor does it appear to be recognized in Michigan. 
About this time the Hamilton invasion began. The species 
t Report of the Geological Survey of Ohio, Vol. II, Part 1, pp. 244, 289-94, 338, 
330, 426, 427, etc. 
2 [bid., pp. 189, 190. 
3 Ibid., Vol. 1, Part 1, p. 144; Vol. II, Part 1, p. 290. 
4 Proceedings of the American Association for the Advancement of Science, Vol. 
XXVIII (1880), p. 298. 
5 Loc. cit., pp. 665, 668. 
6 Grabau, New York State Museum Bulletin No. 92, p. 231. 
