white.] BEAR CEEEK, COLOEADO. 193 



both in the form of the hogbacks that skirt the base of the Eocky Mount- 

 ains and form its foot-hills, and as natural sections in the valley sides of 

 Bear Creek which cuts transversely through them on its way from the 

 mountains to the plains. These rocks are very clearly illustrated in a 

 section facing page 32 of Dr. Hay den's Annual Report for 1874. 



At the time of my visit, Mr. Lakes and Professor Mudge were en- 

 gaged in exhuming some enormous Dinosaurian remains from the west- 

 ern or escarpment face of the principal hogback, a couple of miles north 

 of Morrison. These strata form the member of the section referred to, 

 winch is there designated as " variegated shales," and which immedi- 

 ately underlies the layers of massive sandstone that form the crest of 

 the principal hogback. These sandstone layers are referred without 

 hesitation to the Dakota Group or Cretaceous ISTo. 1, in which reference 

 all other geologists who have mentioned them are understood to agree. 



Upon the discovery of the Dinosaurian remains above referred to, 

 Professor Marsh referred the strata containing them to the age of the 

 TVealden of Europe ;* but in the final publication of his address before 

 the Am. Asso. Adv. Sci. for 1877, he referred them to the Jurassic. In 

 his later conclusion I am much inclined to agree, not that invertebrate 

 paleontology furnishes any direct evidence, but because of the evidence 

 that exists of unbroken continuity of deposition from those strata that 

 are regarded as certainly of Jurassic age with those containing the Dino- 

 saurian remains, called " Atlantosaurian beds," by Professor Marsh.t 



Only a few fossils were collected in this vicinity at the time of my 

 visit; but Mr. Lakes subsequently sent to the office of the Survey a box 

 of fossils which he collected here, containing many species, a list of which 

 is given in an appendix to this report, and they are also included in a list 

 of the fossils of this district, presently to be given, together with notes 

 upon them. 



The fossils of this locality were collected mostly from the strata of the 

 Eox Hills Group; but three species, namely, Inoceramus deformis, I. 

 X>robIematicus,and Ostrea congested are from those of the Colorado Group. 

 These three species were in fact found in some layers of limestone or cal- 

 careous rock at the upper part of the Colorado Group, which no doubt in 

 part represent the Niobrara division of the Cretaceous section of the 

 Upper Missouri Eiver region. 



Search for fossils was prosecuted in the strata of the Table Mountains 

 of this district, which are mainly composed of strata of the Laramie 

 Group, and are capped by a trap outflow. In this search I was not suc- 

 cessful, although the strata are no doubt equivalent with those that 

 were found so fossiliferous in the valleys of Crow and Bijou Creeks. ' 

 Continuing my examination of the Cretaceous strata northward, I visited 

 the valley of Ealstonf Creek, about four miles northward from Golden 

 City. At a locality in the valley of this creek, near the foot-hills and 

 about four miles northward from Golden City, a shaft was sunk several 

 years ago in a search for coal. A bed of lignite was found there which, 

 although not proving profitable for working, is reported to possess about 



* See Introduction and Succession of Vertebrate Life in America, page 17 ; advance 

 copy of Professor Marsh's Address before Am. Assoc. Adv. Sci. 1877. 



t Dr. Hayden referred the exact equivalent of these beds on the Saint Vrains and 

 Big Thompson Creeks to the Jurassic in his annual report for 1873. (See sections 

 facing page 20 of this report.) 



X There seems to be some confusion as to the name of this creek. In the various 

 reports referring to fossils there it is called "Ealston Creek; " but on the maps of the 

 atlas of Colorado it is called "Van Bibber Creek." It is the first creek north of the 

 North Table Mountain, while on the map the name Ealston Creek is applied to the 

 second one north of that mountain. 



13 GS 



