44 WILLIS ELBE. 
more than a few feet. They vary in character from brittle 
masses often of a reddish-brown color, to seams of tough 
admixtures of clay, lime, and sand. All of the members of this 
formation vary laterally in character and thickness. No two 
sections exhibit the same order of succession nor the same 
relative proportion of materials. 
There is, however, one feature which is remarkably persist- 
ent, and which may deserve special mention. Near the base 
of the formation occurs a curious nodular seam of silica resem- 
bling imperfectly formed agates. These are sometimes loosely 
held together, with clay filling the internodular spaces, and 
sometimes gathered into a compact mass. Calcite is also found 
imbedded in the silica. The silica is obviously a deposit from 
solution. In many instances it shows a concentric structure 
‘with bands of different colors. The color varies from deep red 
to light blue.. The seams bearing this agate-like material are 
usually only a few inches thick. Either the seams themselves 
or ‘“‘float’’ from them were noted at nearly every point examined 
in the canyon of the Rio Cimarron, as well as at other localities 
to be described. 
Throughout the extent of the Rio Cimarron, Red Beds occur 
underneath the shale formation. These Red Beds are composed 
principally of deep red to purple sandstones, although more or 
less red shale is interstratified with them. In the upper twenty- 
five miles of the canyon the upper member of the Red Beds series 
is gypsum. In the lower or eastward part the Exeter formation, 
to be described later, takes the place of the gypsum between the 
Red Beds and the shale formation, and lies unconformably upon 
the Red Beds. 
I have previously shown* that the Dakota sandstone extends 
from the Purgatory and its tributary canyons to the Rio Cimar- 
ron and that a shale formation similar to the Dinosaur-bearing 
beds of the Purgatory was found beneath the Dakota. It is 
obvious, therefore, that the protecting sandstone of the Rio 
Cimarron is Dakota. No vertebrate fossils have been found in 
* Jour. GEOL., Vol. 1X, May-June, 1go1. 
