70 Dr. F. V. Hayden on the Primordial Sandstone 
2. Loose layers of very hard ycllow arenaceous limestone with a 
reddish tinge, underlaid by a bed, six to eight feet in thickness 
of very hard blue limestone; the whole contains great quanti- 
ties of broken crinoidal remains with cyathophylloid corals and 
several species of brachiopoda. - - - - 40 ft 
nana, and fragments of a trilobite, Arionellus ? Oweni. 50 to 80 ft. 
- Stratified azoic rocks standing in a vertical position for the 
most part. 
oa 
Leaving the Black Hills in a direction, a little west of south, 
we follow an anticlinal valley to the Laramie Mountains with 
which the Black Hills seem thus obscurely connected. The ev- 
idence, so far as it goes, appears to indicate that the same force 
which elevated the one raised the other, and that the events 
were synchronous. We do not observe the lower rocks after 
leaving the Black Hills until we reach the source of the Nio- 
brara river, where we find a series of horizontal strata resting 
upon the vertical edges of Azoic clay slates and schists, which 
from their lithological characters and position, doubtless belong 
to the age of the Potsdam sandstone, though no organic remains 
could be found. The following section shows the descending 
order of the beds. 
1, Quartzose sandstone, some parts filled with pebbles, —- - 22 f 
2. Red argillaceous slate, - - - - . . . ' 
3. Sandstone, dull reddish ferruginous, like bed 1, above, - ee 
4. A series of strata more or less inclined, composed of gneiss 
with silvery mica in large plates, micacous and talcose slates, 
white quartz, &e. 
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