96 Cincinnati Society of Natural History. 
the bridge, is 4,542 feet, and the highest terrace on the east side is 
4,737 feet, and the highest on the west side is 4,779 feet. The imme- 
diate valley of Bear river may be said to have been worn out ofthe Plio- 
cene or lake deposit. 
Among the lower ranges of hills that border the east side of the 
Great Snake river basin, especially from Port Neuf Canon northward, 
the Pliocene deposits are well shown, and lie beneath the basaltic floor. 
In the Port Neuf Canon this fact is illustrated by the wearing away 
of the cap or floor of basalt, in a number of localities, but on the sides 
of the hills this is shown with equal clearness by the elevations of the 
basalt. The dip of the beds is not great, usually not more than 5° or 
10,° and in all cases in the direction of the great basin. This would 
indicate that there had been a moderate elevation of the mountain 
ranges, or a depression of the basin at a very modern date, even ap- 
proaching very close to our present period. The effusion of such a vast 
amount of igneous matter from the interior of the earth, might suggest 
the possibility, or even probability, that the cause of the subsequent 
changes in the hills around the borders, was either contemporaneous 
or subsequent to the effusion of the melted material. If the elevation 
began with the eruption, it certainly continued long after it ceased, in- 
asmuch as the basalt is lifted up in thick beds, at the same angle with 
the underlying strata. Not only in the valley of the Port Neuf and 
Snake river is the basalt found in conjunction with lake deposits, but 
in numerous localities all over the northwest, it seems to rest upon these 
Pliocene beds, readily adapting itself by the form of the under surface 
to the irregularities of the surface of the lake deposits. 
Prof. Eug. W. Hilgard* divided the Eocene of Alabama and Missis- 
Sippi in descending order, into, lst, Vicksburg Group, 120 feet; 2d, 
Red Bluff Group, 12 feet; 3d, Jackson Group, 80 feet; 4th, Claiborne 
Group, 60 feet; 5th, Buhrstone Group, 150 feet; 6th, Flatwoods and 
Lagrange Lignitic Group, 450 feet, making a total thickness of 872 
feet. The Lagrange and Porter’s Creek Group of Safford is the same 
as the Flatwoods and Lagrange Lignitic. The Buhrstone Group of 
Tuomey is the same as the Siliceous Claiborne Group of Hilgard. 
The Kocence is followed by the Grand Gulf Group, probably a de- 
posit in brackish water, almost non-fossiliferous, and having a thickness 
of 250 feet. 
Prof. Leo Lesquereuxt described, from the Green River Group of 
* Proc. Am. Ass., Ad. Sci. 
+ 1872, U. S. Geo. Sur. of Montana, ete. 
