NATURAL SCIENCES OF PHILADELPHIA. 
149 
Subdivisions. 
Localities. 
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I— I 
12 
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1st, dark gray or brown sand, loose, 
incoherent, with remains of Masto- 
don, Elephant, &c. ; 2d, sand and 
gravel, incoherent ; 3d, yellowish 
white grit, with many calcareous, 
arenaceous concretions ; 4th, grey 
sand with a greenish tinge ; contains 
the greater part of the organic re- 
mains; 5th, deep yellowish red arena- 
ceous marl ; 6th. yellowish gray grit, 
sometimes quite calcareous, with nu- 
merous layers of concretionary lime- 
stone from two to six inches in thick- 
ness, containing fresh water and land- 
shells, Succinea, Limnea, Paludina, 
Helix, &c., closely allied and perhaps 
identical with living species ; also 
much wood of coniferous character. 
Covers a very large area 
on Loup Fork, from the 
mouth of North Branch to 
source of Loup Fork ; also 
in the Platte Valley. Most 
fully developed on the Nio- 
brara river, extending from 
the mouth of Turtle river 
three hundred m.iles up the 
Niobrara. Also on Bijoux 
Hills and Medicine Hills. 
Thinly represented in the 
valley of White river. 
Usually a coarse grained sandstone, 
sometimes heavy bedded and com- 
pact ; sometimes loose and incoher- 
ent ; varies much in different local- 
ities. Forms immense masses of 
conglomerate ; also contains layers 
of tabular limestone with indistinct 
organic remains ; very few mam- 
malian remains detected, and those 
in a fragmentary condition. Passes 
gradually into the bed below. 
Most fully developed 
along the upper portion of 
Niobrara river and in the 
region around Fort Laramie. 
Seen also on White river 
and on drindstone Hills. 
A dull reddish brown indurated 
grit, with many layers of silico-cal- 
careous concretions, sometimes form- 
ing a heavy bedded fine grained sand- 
stone ; contains comparatively few 
organic remains. 
Niobrara and Platte rivers ; 
well developed in the re- 
gion of Fort Laramie ; also 
in the valley of White river, 
conspicuous, and composing 
the main part of the divid- 
ing ridge between White 
and Niobrara rivers. 
Very fine yellow calcareous sand, 
not difl'ering very materially from 
Bed D, with numerous layers of con- 
cretions and rarely organic remains, 
passing down into a variegated bed, 
consisting of alternate layers of dark 
brown clay and light grey calcareous 
grit, forming bands, of which I 
counted twenty-seven at one locality, 
varying from one inch to two feet in 
thickness. 
White river, Bear creek. 
Ash Grove spring. Head of 
tihyenne river. Most con- 
spicuous near White river. 
1858.] 
