WHITE. J BEAR CREEK, COLORADO. 193 



both ill the form of tlie liogbacks tliat skirt the base of tlie Eocky Mount- 

 ains and form its foot-liills, 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 m a 

 section facing page 313 of Dr. ria>den's Animal Eeport for 1874. 



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

 gaged in exhuming some enormous Dinosaiman remains from the west- 

 ern or escari)ment face of the principal hogback, a couple of miles north 

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

 which is there designated as " variegated shales," and Avhich 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 jSTo. 1, in which reference 

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



Upon tlie discovery of the Dinosaiirian remains above referred to. 

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

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

 the Am. Asso. Adv. Sci. for 1877, he referred them to the Jm-assic. In 

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

 jialeontology 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 Diuo- 

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



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

 visit ; but Mv. Lakes subsequently sent to the ofdce 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 

 uiion them. 



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

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

 jn'ohlematicits, and Ostrea congesta^ are from those of the Colorado Group. 

 These three spe(;ies 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 trail 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 l\alston| Creek, about foiu* 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 Citj^, a shaft was sunk several 

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

 although not proving iirofitable for working>is reported to possess about 



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

 cojjy of Professor Marsh's Address before Ani. Assoc. Adv. Sci. 1877. 



tDr. II ayden referred the exact equivalent of these beds on the Saint Vrains and 

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

 facmg page 20 of this report.) 



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

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

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

 North Table Mountain, while on the maj) the name Ralston Creek is apidicd to the 

 second one north of that mountain. 



13 as 



