204 EEPOET UNITED STATES GEOLOGICAL SUEVEY. 



fully double that of those in the plains at the eastern base of the Front 

 Eange, but not greater than' that at the western base of the Park Range. 

 The Middle Park strata contain no fossils that are certainly identical 

 in species with any of the numerous forms found on each side of that 

 region at the eastern and western bases, respectively, of the Eocky 

 Mountains ; and they contain, so far as known, only those imperfectly 

 known species before referred to that are possibly identical with forms 

 in the Fort Union beds of the Upper Missouri. 



So far as I am aware, no coal has been found in the Laramie beds of 

 Middle Park, while it is more or less abundant in all the other known 

 regions of that groui3. 



In connection with this latter fact it may be mentioned that Mr. Mar- 

 vine found a bed of coal in the Fox Hills strata of Middle Park, and it 

 is well known to exist in strata of that age west of the mountains, 

 but none has ever been found in >^trata of the same age east of the 

 mountains in Colorado, so far as I am aware. 



Leaving'^ Middle Park I crossed the Park Eange to the headwaters of 

 Yampa Eiver, by way of Egeria Park. 



Owing to want of time, comparatively little was done in the examina- 

 tion of the Cretaceous Groups of Middle Park, except to identify them 

 as unmistakably equivalent with the groui)s of that period as recognized 

 elsewhere in Colorado, both east and west of the Eocky Mountains. In 

 my generalizations, I shall therefore make use of the observations that 

 have been made by Hayden, Powell, and Marvine in this district. I 

 foimd limited exposures of these grouiDs in connection with the Laramie 

 Group in the vicinity of Hot Sulphur Springs in the middle portion of the 

 park, and also farther westward. Passing do^ni the valley of Grand 

 Eiver, only the Lake Beds were observed within immediate view from my 

 line of travel, until we reached the valley of Muddy Eiver, a northern 

 tributarj^ of the Grand, that has its course along the western portion of 

 the i)ark. Here the strata of the three Cretaceous Groups are exposed 

 along the valley of the Muddy and also flanking the neighboring eastern 

 base of the granite nucleus of the Park Eange, the Eed Betls only inter- 

 vening. Crossing their outcrops, I x>assed over the Park Eange into 

 Egeria Park, where I found, at the western base of the range, as at its 

 eastern base, the Eed Beds resting ui^on the granite, and these in turn 

 overlaid by the Dakota and Colorado Groups. 



The strata of the latter groups occupy nearly the whole of Egeria 

 Park as well as an adjacent part of the valley of the Yampa, but they 

 are here and there capped with basalt, consisting of shreds of the great 

 sheet that once doubtless covered the whole region of the headwaters of 

 the Yampa and White Elvers. The strata of the Colorado Group in 

 the park and adjacent neighborhood consist largely of light colored 

 sandstones, often only slightly compacted. In some parts, however, the 

 group here consists of the characteristic bluish sandy shales. 



After j)assing a few miles down the valley of the Yampa, we crossed 

 over in a northwesterly direction, to Terrible and Sage Creeks. In the 

 valley of the last-named creek, near the crossing of the wagon road, I 

 found an exposure of Cretaceous strata. Judging from their lithological 

 aspect I was at first disposed to regard them as belonging to the Colo- 

 rado Group, but the position of the outcrop, not more than 200 feet be- 

 neath the base of the Laramie Group, the strata of which are seen in 

 the adjacent hills, forbade such a reference. The exjiosure consists of 

 about thirty feet in thickness of light-bluish, grayish, and dark carbon- 

 aceous shales, with occasional compact concretions of calcareous and 

 argillaceous rock. In these concretions I obtained the fossils of the fol- 

 lowing hst, most of which are of well-known species. 



