mingled with those identical with recent ones ; _ a few Mollusca, 
mostly identical with recent species, so far as determi 
Most fully developed along the Missouri River, from the mouth of the 
Niobrara to St. Joseph ; also in the Platte Valley and on the Loup Fork. 
Thicknees, 300 to 500 feet. 
Pliocene Tertiary. —Bed F.—\st, dark gray or brown sand, loose, 
coherent, with remains of Mastodon, Elephant, &e.; 2d, sand and ie, 
, yellowish gra 
of coneretionary Hmestone from two to six inches in thickness, contain- 
ing fresh water and land shells, Succinea, Limnea, Paludina, Helix, &c., 
closely allied and ob identical with living species; also much wood 
of ee charac 
Cove very ee area on Loup Fork, from the mouth of North 
: Bran at $5: source of Loup Fork; also in the Platte Valley. Most fully 
: developed on the Niobrara River, extending from the mouth of Turtle 
. River three hundred miles up the Niobrara. Also on Bijoux Hills and 
Medicine Hills. Thinly represented in the valley of White River. 
ickness, 300 to 400 fee te 
Miocene—Bed E. —Usually a —— re sa sometimes 
ee heavy bedded and compact; sometimes loose and incoherent; varies 
much in different localities. Forms immense masses of conglomerate ; 
also contains layers of tabular limestone with indistinct organic re- 
mains; very few Mammalian remains d and those in a frag- 
mentary condition. Passes gradually into the bed below. 
Most fully developed along the pad _— of the Niobrara River, 
d in the region around Fort Laramie. Seen also on White River, 
and on Grindstone Hills. 
Thic kn ~ ee 
¢ ark brown clay and light gray calcareous grit, forming bands, 
I naa vorted ce esti at one locality, ie frei one inch to 
feet in thick é 
‘ite River, Bear Creek, oo _ Spring, Head of Shyenne River. 
five as and Oreodon Bed, B—A deep flesh-colored argillo- 
careous 3 Sdurated grit; the outside when W has the : 
e of a plastic clay, Passes down into a gray clay, with layers of 
