PETERSON: A-REVISION OF THE ENTELODONTIDA 75 
horizon of the Miocene exposed along the upper Niobrara, should be regarded as 
the base of the middle Miocene, or a horizon filling, in part at least, the hiatus 
between the lower and the middle Miocene. Places of non-conformity between the 
upper and lower Harrison beds are frequently found, the first of which observed by 
the writer in 1901 is situated immediately east of the Niobrara-Wyoming State line. 
tr 2 POON BUTTE 
5 Z s 3ro0n Spree Beds 
fe AGATE. SPRING QUARRIES § Nips Bede 
45 kes np Lower Harrison Beds 
YY UY) Sif + 
YT ff ge) 
N LLU Ma YU oh “ Monroe Creek Beds 
300,t 
Gering Beds 
200ft 
Oligocere Beds 
Is oft 
Squaw Creek 
Fic. 27. Diagrammatic Section of the Miocene Beds in Western Nebraska and Eastern Wyoming. 
This is in reality the type locality of the upper Harrison beds, which were called 
to J.B. Hatcher’s attention by the writer in 1901. Hatcher, then Curator of 
Paleontology of the Carnegie Museum, decided these beds to be the “ Nebraska 
beds” of Scott. Viewing these beds from the standpoint of certain portions of the 
fauna (81, p. 56) taken together with lithological characters, the sediment being 
usually of a darker color, it would seem that a natural division between the lower 
and middle Miocene may be established at the contact of these two horizons. 
As has been stated elsewhere (80, p. 487; 81, p. 41) the Agate Spring Fossil 
Quarries are located in the lower Harrison beds. The origin of the deposit in which 
the fossil bones of these quarries are found is most likely a stream deposit. In -sup- 
port of this view may be cited the fact that the parting plane underneath the layer 
carrying the bones is a few shades darker in color than that layer itself, and the 
sone Lhver 
tt —_[Monopus! pones | 
ea Pillars of pinkish sand coluely barren of fossils 
ne 
Hard, light colored concretions 
Fig. 28. Section of Face of Quarry of University of Nebraska at the End of the Season of 1908, showing channels in the 
stratum supporting the fossiliferous layers. The Nos. 1-20 indicate sections 5 ft. in length. 
bones are often closely packed in irregular channels and pockets, which vary in 
thickness from two or three to eighteen or twenty inches (8 to 50 em.). The sur- 
faces of the bones are sometimes highly polished and worn, and there are numerous 
