196 Bulletin of Lahoratofies of Denison University [Voi.xi. 
Upper Cretaceous, ranging from the Dakota to and including 
the Laramie. 
Newberry estimates the total thickness of the strata in New 
Mexico to be about 3500 ft. and divides it into the Upper, Mid- 
dle, and Lower Divisions, corresponding respectively to the 
Montana, Colorado, and Dakota formations given above. (See 
Macomb’s Expl. Exped. Geol. Report, pp. 121, 122.) 
In the Colorado and New Mexico Cretaceous strata it was 
found very difficult to discriminate between the shales of the 
Ft. Benton and those of the Ft. Pierre Groups. For this rea- 
son Mr. Clarence King proposed the new term Colorado Group 
“for the great clay group ” of the Cretaceous in this region. 
But it has been found that it is just about as hard to apply the 
lithologic classification of the formations to this new group as it 
was to the older ones of Meek and Hayden. For this reason 
Dr. C. A. White in describing the Cretaceous formations of 
Colorado used the same nomenclature as Mr. King, but applied 
the term Colorado Group only to the Niobrara and Ft. Benton 
Groups, and placed the Ft. Pierre in the Fox Hills Group. 
This has been further improved upon by Mr. G. H. Eldridge, 
who adopted the same divisions as Dr. White, but changed 
the Fox Hills and Ft. Pierre Groups to that of the Montana 
Group, thus doing away with the confusion caused by using the 
term Fox Hills Group in two different senses. (See Eastern 
Colo. Section, below.) 
The Pacific Border Region. This is a very long and nar- 
row strip running along the coast from the southern boundary 
of California through Oregon and Washington into British Co- 
lumbia. Both the Upper and Lower Cretaceous are repre- 
sented. The following section is the one which was adopted 
by the California State Survey : 
( Tejon Group. 
Upper Cretaceous < Chico Group. 
( Wallala Group. 
Lower Cretaceous Shasta Group. 
The following section. Meek and Hayden’s Upper Missouri 
River Section, we give in full. This section has long been con- 
