THE EOCENE PLATEAU. 
15 
south, its upper beds reach the level of the bottom at about the middle of 
the length of the canon. Above them, softer beds appear, alternating with 
strata of sandstone; the beds are first gray, but others soon appear which 
are striped with red. The red-striped marls increase in relative thickness 
toward the west, and the sandstone strata diminish, until, at the head of the 
canon, the highlands fall off into hills of bright-colored marls eroded 
into rounded and picturesquely-formed masses. These extend in a 
long line to the north and south, facing westward. To the west, a wide, 
elevated plain spread before us, varied with a few hills, and stretching away 
with a gentle slope to Canon Largo and the country of the San Juan 
River. The discovery of the variegated marls was one of no little interest 
to the writer, inasmuch as I had made special efforts to find Eocene beds in 
this region, and they were then crowned with success. The position of these 
marls, with their close physical resemblance to the Wahsatch beds of Bear 
River, Wyoming, together with the evidence furnished by a lower molar 
of Coryphodon, found by my guide, indicated that I had discovered the 
sediments of the great body of fresh water which during successive stages 
of the Eocene period occupied the drainagerbasin of the Great Western 
Colorado. The thickness of the strata exhibited in the walls of the Canon- 
cito de las Yeguas, I estimated at 1,200 feet. 
On leaving the mouth of this cation, and proceeding southward, the 
southern dip of the red sandstone brings their summit to the ground-level 
in about ten miles distance. The red and gray marls, with alternating beds 
of white and yellowish sandstone, appear on their summits, and at a point 
twenty miles south of the canon form a mass of bad-land bluffs of from 
600 to 1,000 feet elevation. This escarpment retreats and then turns to the 
east, forming an extensive horseshoe, the circumscribed area being occu¬ 
pied with hills and picturesque masses of sediment, with all the peculiar 
forms and desolation of b.ad-land scenery. I remained in camp for about 
a month near this circle, and obtained many fossil remains of Vertebrata. 
Ten miles south of this point, another horseshoe of bad-lands covers an 
extensive area, and proved to be as rich in fossil remains as the first. Here 
I made my second camp, remaining in it for three weeks. The southern 
boundary of the northern tract extends to within six miles of the Cretaceous 
