STRATIGRAPHIC POSITION OF JUDITH RIVER FORMATION 753 
polation of the true Laramie between the Fox Hills and the Black 
Buttes beds, which are referred by us to the post-Laramie; and 
the placing of the Arapahoe and Denver below the Lance, reversing 
the position given them by Lull and the reference also of the Judith 
River beds to the Lance. This arrangement appears to me not 
only the true one but far better, as it ties the species together in a 
more logical manner. It will not be necessary to conclude as Lull 
has that the “identification of Ceratops montanus seems hardly 
possible, as Ceratops montanus is a Judith River type and is vastly 
older than the Arapahoe.” Although the Arapahoe and Denver 
lie at the bottom of the series and the Hell Creek beds nearer the 
middle or at the top of the Lance formation, we do not yet know 
their exact equivalency, but that they are not separated by thou- 
sands of feet of beds can confidently be stated. Mr. Cross, long 
ago, pointed out “the fact that the Judith River strata may perhaps 
represent the Arapahoe or some other post-Laramie formation.’ 
Eliminating from Hatcher’s list of Judith River vertebrates 
(which includes no mammals in the type region) all the species 
which are duplicated under other names and all which come from 
beds not of Judith age or that occur outside the typical area (the 
Judith basin of Montana), his list is reduced to 33. Of these we 
find that 22 occur also in strata referrred to the Lance formation. 
These species are tabulated below. Besides the Converse County, 
Wyo., and Hell Creek, Mont., lists, others might be given showing 
that Judith River species occur in other parts of Montana as well 
as in northeastern Colorado, but the lists given here are deemed 
sufficient to prove the identity of the beds. 
Writing in 1902 (and the list was not so great then as now) on 
the identity of genera and species not only between these beds but 
including also the Belly River of Canada, Williston says: 
It would seem almost incredible that so many of these should have per- 
sisted unchanged through the long interval represented by so many thousand 
feet of Fox Hills deposits, to say nothing of those of the Fort Pierre. I doubt 
if a parallel can be found elsewhere in vertebrate paleontology. It is true 
that many of these forms from both the Judith River and the Laramie [Lance] 
* Monograph U.S. Geol. Surv., XXVILI (1896), 230. 
2 Science, N.S., XVI (December 12, 1902), 953. 
