“Mesozoic and Cenozoic Geology and Paleontology. ike 
Springs on the North Platte westward toward the Sweet Water moun- 
tains, and near the divide between the North Platte and Wind river 
they reach a thickness of 400 feet. From this divide throughout the 
Wind river valley they occupy the greater portion of the country, and 
though inclining in the same direction with the older strata the beds 
do not dip more than from 1 to 5 deg. They differ from the other de- 
posits in the great. predominance of arenaceous sediments, and in the 
absence of vegetable remains, but they contain fragments of turtles 
and numerous fresh-water and land shells. The entire thickness of 
these deposits is estimated at from 1,500 to 2,000 feet. 
The White River Tertiary beds extend southward along the Laramie 
mountains to Willow Springs, and up the North Platte to Box Elder 
creek, and beyond in small outliers, showing that much has been re- 
moved by erosion. From the source of Box Elder creek, they extend 
to the head of Bates Fork, and westward to the Medicine Bow 
mountains. ‘These beds for the most part, hold a horizontal position, 
while those of the lignite age are much disturbed; moreover, their 
position shows that they are of much more recent origin. The White 
river Tertiary deposits are followed by the White river bone beds, 
which pass up into the Pliocene of Niobrara by a slight physical 
break, and the latter are lost in the yellow marl or Lacs deposits. 
Meek and Hayden* made a vertical section of the Tertiary rocks 
of Nebraska, in ascending order as follows : 
1. Wind river deposits, consisting of light gray and ash-colored 
sandstones, with more or less argillaceous layers. Thickness from 
1,500 to 2,000 feet. Found in the Wind river valley and west of the 
Wind River mountains. 
2. The White River Group, consisting of white and light drab 
clays, with some beds of sandstone and local layers of limestone. 
Thickness 1,000 feet or more. Found on the Bad Lands of White 
river ; under the Loup river beds, on Niobrara, and across the country 
to the Platte. Age of the Miocene. 
3. Loup river beds, consisting of fine loose sand, with some layers of 
limestone. Thickness, 300 to 400 feet. Found on Loup fork of Platte 
river, and extending north to the Niobrara river, and south an un- 
known distance. Age of the Pliocene. 
They described from the Wind River Group, in the Wind river 
valley, Helix veterna, and H. spatiosa, now Macrocyclis spatiosa. 
* Proc. Acad. Nat. Sci., vol. xii. 
