652 A. C. PEALE 
In the accompanying correlation table of local sections the line 
of unconformity between the Cretaceous and Tertiary is shown by 
the double line, which, in Colorado, indicates the break between the 
Arapahoe and the Laramie, and in other localities represents the 
erosional interval between the Lance and Laramie wherever the 
two are in contact as seen by Dr. Knowlton and the writer on the 
North Platte River near the mouth of Medicine Bow River in 
Wyoming. It marks also the greater stratigraphic hiatus noted 
in all sections made up to the present time in Montana where the 
Laramie is absent; and where either the Lance or the Judith River 
is in contact with the Fox Hills or where this also is absent with 
the Pierre, all of these conditions are shown graphically in this sec- 
tion. The sections in the Dakotas are not given, but there, as 
already stated, the Lance is sometimes in direct contact with the 
Pierre, as in the section given for Willow Creek, Mont., or with the 
FoxHills beds, the thickness of which varies according to the amount 
that has been removed by erosion. This need only be referred to 
here, as the whole subject has been thoroughly treated by Dr. 
Knowlton in his two papers on the stratigraphic position of the 
Lance formation.’ It is necessary to state here only that the writer 
is in perfect agreement with Dr. Knowlton? as to the position of 
this unconformity and its being the place at which to draw the line 
between the Cretaceous and Tertiary, and further, to reiterate 
that the Judith River formation is the direct equivalent of the 
Lance formation, not only from its paleontological contents, as 
will be shown later, but also from its stratigraphic position as shown 
in the section given above. 
t Proc. Wash. Acad. Sci., XI (1909), 179-238; Jour. Geol., XIX, No. 4 (May- 
June, 1911), pp. 358-76. 
2 Jour. Geol., XIX, No. 4 (May-June, tort), p. 376. 
