234 F. V. Hayden on the Geology of the Country 
would be found forming an outcropping belt all along the eastern 
slope of the Rocky Mountains. After leaving the Black Hills 
we next observed it along the margins of the Big Horn range 
near the summit, holding the same relative position and exhibit- 
ing the same lithological characters. A few thin layers of fine 
calcareous sandstone were observed filled with fossils charac- 
teristic of this period. At the head of LaBonte creek in the 
Laramie range I noticed a bed resting discordantly upon azoic 
slates, fifty to one hundred feet in thickness, holding the same 
position and possessing the same lithological characters which 
it reveals at other localities. I could discover no fossils in it 
at this point but I am confident that this bed represents the 
Potsdam sandstone. The same bed seems to occur all along 
the mountains from Laramie Peak to Cache la Poudre creek un- 
derlying the well-known Carboniferous strata and resting upon 
ecomposing granitoid rocks, which form the nucleus of the 
la Poudre, a distance of over one hundred miles. It was also 
seen along the eastern slope of the Wind River mountains but 
in the 
position. 
Sometimes they are n 
the Laramie and Platte R 
a that they have either been removed b 
y 
are alternate layers of sandstone 
stones, many of which show obl 
