882 The American Geologist. June, 1897 
were unable to continue to live in the mud-bringing, moving- 
water and gave pla(?e to other forms thriving under the new 
condition. 
The differences between the Trenton and Utica formations, 
as established in New York state, are not local or prevailingly 
lithological. This fact, as well as others valuable to the under- 
standing of the nature of the motion of the water are excel- 
lently presented in the papers of Walcott on the Utica slate.* 
That author states that from lake Huron, across the province 
of Ontario to New York state and thejice by way of the 
Black river, Mohawk, Hudson, lake Champlain, St. Lawrence 
valley to Anticosti and from the valley of the Hudson to Vir- 
ginia the ditferences between the Trenton and Utica forma- 
tions are essentiall}'^ the same. The black bituminous shale 
forms a distinct horizon above the Trenton. Thus it becomes 
apparent that the change in the physical conditions which in- 
augurated the Utica epoch in the Mohawk region extended 
over a wide area, along the southern and eastern coast of the 
then existing land and over the site of the present Appalach- 
ian mountain system. 
It must be added that the alternations of limestone beds and 
shales in the upper Trenton and lower Utica shale are also 
widely extended. Cushingf expressly mentions the shaly 
intercalations in the Trenton limestone on the shores of lakes 
George and Champlain while the Geology of Canada;]; reports 
that "the liniestones of the Trenton formation are generally 
separated by thin layers of black or blackish brown bitumi- 
nous shale. The layers in some places become thicker to- 
wards the top and present a passage to the succeeding de- 
posit," the Utica shale. § 
*C. D. Walcott: The Utica slate and lelated Formations; cf. above. 
C. D. Walcott: The Value of the Term— Hudson River Group. Bull, 
of Geol. Soc. of Am., vol. i, pp. 335-356. 
tRep. of the State Geologist for 1893, p. i83-486. 
iGeology of Canada, p. 198, 1863. 
§Walcott reports that there are no limestone intercalations in the 
180 feet of Utica shale, measured by him in Jefferson covinty, (east of 
lake Ontario). A like observation has been made by the writer near by, 
in Lewis county. As there, however, the shaly intercalations of the 
upper Trenton are quite conspicuous it seems essentially a question as 
to the drawing of the line of separation and it is possible that there the 
Trenton conditions continued a little longer and terminated more sud- 
denly. The reappearance of a Trenton-like bed in the series of passage 
beds on East Canada creek is certainly indicative of such a possibility. 
