102 CARBONXKKKOUS FORMATIONS AND FAUNAS OF OOLOKADO. 



be given to it, and the fossils themselves can not be found. A small collection 

 supposed to belong to the same horizon was obtained somewhat farther north, at 

 Lyons, Imt it jH-oves (o be of little value in determining the questions at issue. It 

 would lie impossible to form fi-om it a well-founded opinion as to whether the age is 

 JNIesozoic or Paleozoic. A minute gasteropod, resembling Natica or Nat! cops i.i, was 

 obtained, and some small pelec3"pods, suggesting bj^ their shape several Paleozoic and 

 Mesozoic genera. While on one hand the gasteropod is probably distinct from Natica 

 Mia, with which one would hrst compare it, it is at the same time at present unknown 

 in the Minnekahta fauna. The pelecypod also appears not to occur there. Though 

 it ma}- be the same as some indeterminable forms from the Black Hills, I believe, so 

 far as the poor preservation justifies an opinion, that it is distinct. Paleontologic 

 evidence, therefore, if given any weight at all in this instance, seems to be somewhat 

 adverse to this correlation, which, based upon little but lithology and stratigraphic 

 occurrence, can not under existing conditions be given unreserved acceptance. 



Darton further says of the horizon from which he obtained fossils at Morrison 

 that it was traced southward for some distance, until lost in the coarse sandstones of 

 the Garden of the Gods. These sandstones, however; are supposed to represent the 

 Fountain formation, and to occur stratigraphically entireh' below the Wyoming, or 

 to be equivalent to some of the lower beds included in it in certain sections. 



One of the earliest reports which relate to the geology of Colorado, and perhaps 

 the earliest whose scope and method give it real scientific value, was Hayden's 

 account of the geology and natural history of the Upper Missouri." This is the first 

 of a number of papers from the pen of the same author iu which the geology of this 

 portion of Colorado is discussed, but the later ones mark but little advance, so far as 

 the Paleozoics are concerned, over this earliest contribution. The map which accom- 

 panies this report, and the report itself, extend sufficiently far west to include the 

 northern half of the Front Range in Colorado and its extension into W^^oming, 

 though the chief field of observation was farther east. Haj'den maps a continuous 

 strip of Lower Silurian, Carboniferous, Permian, and Red Beds strata (which are 

 here referred to the Jurassic) along the eastern flank of the Front Range from 

 Laramie Peak southward to Pikes Peak. Of the existence of these series to the 

 north and east Hayden had more or less satisfactory paleontologic evidence. Their 

 identification along the Front Range was influenced by the idea that the sequence 

 there was complete and unbroken, and was in most cases dependent upon similarity 

 in lithologic characters or evidence still less appreciable. 



The Lower Silurian of the Front Range is apparently the red sandstone and 

 limestone underlying the fossiliferous Carboniferous limestones which play out just 

 south of Colorado's northern line. King,* it will be remembered, later compared 



a Am. PWl. Soc, Trans., vol. 12, n. s., 1863, pp. 1-219. 

 b U. S. Geol. Expl. 40th Par., Kept., vol. 1, 1878, p. 129. 



