148 
PROCEEDINGS OF THE ACADEMY OP 
notice its occurrence in tlie only locality where it was observed during tlie 
explorations of the past year, near the source of the South Fork of the Shyenne 
river. It here rests conformably upon Cretaceous bed No. 5, and in no place 
exhibits any indications of having been disturbed by the subterranean forces 
which have wrought such changes in the physical features of this region. The 
following section will represent the descending order of the beds as seen at this 
locality : 
€. — Yellow arenaceous bed, holding the same position, I think, as the one at 
Fort Clark, which contains numerous fresh water shells. 
d. — Light gray grit, with numerous iron-rust concretions, same bed, seen on 
Cherry Creek, Fort Clark, on the Missouri above Fort Union, and on the 
Yellow Stone, 20 to 30 feet. 
c. — Very impure Lignite, . . . . . . , 4 to 6 feet. 
h. — Dark ash colored clay passing up into the Lignite, ... 20 feet. 
a. — Fine yellow sand : about 6 feet exposed. 
By reference to the colored map, the boundaries of this great basin will 
once be seen north and east of the Black Hills. It will also be seen that mj 
former explorations show its full development on the Yellowstone, as high uP 
as the mouth of the Big Horn river. It will then appear probable that its 
existence on the South Pork of the Shyenne indicates its extension from the 
Yellowstone, along the western base of the Black Hills, and that it adapts itself 
to the rugged features of the country, caused by the upheaval of the older 
formations, in the same manner as the Miocene Tertiary near Raw-Hide Peak 
and Laramie Peaks. 
2d. Tertiary Basin of White and Niobrara Rivers. 
In St, former paper* I gave a vertical section of the different beds of this 
basin as far as they were known at that time. During the past year, many 
Additional fa-cts, and a large collection of new organic remains have been 
secured, which enable me to present a section more accurate and complete. 
It will be at once apparent from the list of localities for the different beds, how 
extensive a geographical area this basin occupies. 
Vertical Section^ showing the order of superposition of the different beds of the 
Tertiary Basin of White and Niobrara Rivers. 
Subdivisions. 
Localities. 
Yellow silicious marl, similar in its 
character to the loess of the Rhine, pas- 
sing down into variegated indurated 
clays and brown and yellow fine grits ; 
contains remains of extinct quadru- 
peds, mingled with those identical 
with recent ones ; alsoafewMoUusca, 
mostly identical with recent species 
so far as determined. 
Most fully developed along 
the Missouri river, from the 
mouth of the Niobrara to 
St. Joseph ; also in the Platte 
Valley and on the Loup Fork. 
♦Netes on the Geology of the Mauvaises Terres of White River. Proceedings of 
the Academy of Nat, Sc. Philadelphia, June^ 1857. 
[[June, 
