154 
PROCEEDINGS OF THE ACADEMY OP 
ren, presenting its usual lithological characters, and containing bones and 
teeth of the animal from which it derives its name. The following section of 
strata, in descending order, will show the details of this upheaval. 
g. — Layers of whitish oolitic limestone, doubtless Tertiary. 
f. — Compact ferruginous sandstone, ...... 80 feet. 
e. — Yellow friable sandstone, ....... 2 feet. 
d. — Light gray fine clay, ........ 4 feet. 
c. — Yellowish white sandstone, quite friable, .... 5 feet. 
h. — Drab or ash colored indurated clay, passing down into red clay, 6 feet. 
a. — Variable incoherent clays, red, yellowish, &c., which may be of Jurassic 
age, 50 feet. 
Passing down the valley toward the Shyenne, the Tertiary beds disappear, 
and the Cretaceous bed No. 5 occupies the country. At one locality an up- 
heaval was observed, exposing all the subdivisions of the Cretaceous rocks, as 
will appear from the following section : 
No. 5. Presenting its usual lithological characters, with numerous fossils ; 
strata but slightly disturbed, 100 to 150 feet. 
No. 4. Presenting same characters as on the Missouri river, . 100 feet. 
No. 3 150 feet. 
No. 2 200 feet. 
No. 1 250 to 300 feet. 
No. 5 is but slightly disturbed, as will be seen by examining the illustrative 
section. Nos. 4, 3 and 2 present only the vertical edges of this strata, across 
which the above measurements were taken. The strata of No. 1 seem to have 
been elevated so as to retain a nearly horizontal position. No. 3 at this locality 
contains numerous fossils, the most abundant of which are Ostrea congesta ^nd 
Inoceramus prohleynaticus. This bed does not present altogether the same 
lithological character as on the Missouri river, but possesses a more laminated 
and gritty structure, sometimes approaching to a calcareous sandstone. Cross- 
ing the Shyenne, on our way northward, we have the commencement of a series 
of ridges of upheaval, which surround the Black Hills. 
I could not ascertain that there was any regularity in the dip and strike of 
the strata, each ridge or local upheaval ditFering from the other in that re- 
spect. As we approach the southern base of the Black Hills, the strata incline 
very nearly to the southeast. No. 1 does not appear, but we have a fine de- 
velopment of No. 2, possessing all its characteristics of plastic clay, with ash- 
colored grit concretions, containing an abundance of well preserved fossils ; 
No. 3, with large quantities of 0. congesta and /. problematicits, in an exceed- 
ingly comminuted condition ; No. 4 also appears, and No. 5 caps the hills on 
all sides. Nos. 2 and 3 are exposed only by the upheaval. On a branch of 
Beaver creek we find No. 2. one hundred and fifty to two hundred feet in thick- 
ness, and presenting its usual characters in full. 
Inasmuch as the principal facts relating to the Geology of the Black Hills 
have already been discussed, I will omit the details of our exploration of them, 
and pass on to a description of the country along our route, from Bear Peak, 
on the north eastern base of the Black Hills, to the entrance of the Niobrara 
river into the Missouri. 
Near Bear Peak, No. 2 is quite largely developed, presenting its usual litho- 
logical characters, and containing great quantities of fish remains, but no other 
fossils were seen in it. No. 1 is composed of variegated clays, grits and sand-, 
stones, with indistinct vegetable-impressions, fossil wood, and a few unchar- 
acteristic Saurian bones. No. 3 is also exposed by the upheaval of the beds, 
with its usual fossils, but possessing the character of a laminated calcare- 
ous sandstone, instead of the soft homogeneous calcareous marl of the Mis- 
souri river. From thence to the Shyenne, No. 4 forms a surface of the coun- 
try, for the most part undisturbed. 
I will not here dwell upon the influences which the eroding power of water 
must have exerted, in modifying the physical features of the country in and 
[J une, 
