12 C'ARHONIFKKOUS FOKMATIOMS and faunas of (UIJ.oUAUO. 



silliic liclil liy the siimc geologist and otlicrs coining jii'tci', \\iis at tiic tiinc a real and 

 iiiil)oi'tant coiiti'ilmtioii to tlu- geologic literature of Colonulo. 'i'liis report, .so I'ai' 

 as it relates to this sii))ject. deals with the formations <>xposed along the eastern 

 margin of the Front Range. In IStiS appeared twoothei- papers by the same authoi- 

 dealing with the same subject, which will l)e referred to in the resume of historical 

 geology. 



llayden's third annual report, jjublished in 1869 and afterwards reprinted, gives 

 an ai'count of a hasty but extended trip through eastern Colorado and New Mexico, 

 which is reviewed in the resume, to follow. 



In 1874 appeared the first of a series of four reports in which the geology of the 

 entire State was outlined by means of reconnaissance explorations systematicall\' 

 plainied. The discussion of the material contained in these reports forms one of the 

 most important pai'ts of my resume. The one which apjDeared in 1874 is the seventh 

 of the annual reports of the Hayden survey. It contains reports by Hayden, End- 

 lich, Peale, and Marvine. The same year saw the publication of Ruffner's report on 

 the geology of the Ute country. A topographic map of a large portion of Colorado 

 accompanies this report, the text of which is largely descriptive of geographic and 

 other features. Brief geologic reports by F. Hawn and L. Hawn accompany it, 

 dealing chiefly with the Sangre de Cristo, Elk, and San Juan mountains. This will 

 be discussed in more detail below. 



In 1875 was published the third volume of the final reports of the Wheeler sur- 

 vey, containing a description bj^ Stevenson of a verj' extensive area in central Colo- 

 rado examined during the year 1873. This will be considered in detail later on. 

 The same is true of a report by Cope on northwestern New Mexico, in which, how- 

 ever, the geology of a portion of Colorado is incidentalh' considered. Endlich 

 discusses the mines and geology of the San Juan country, in which, though the 

 sedimentar}' beds are not described in the text, Carboniferous limestone and Car- 

 boniferous sandstone are represented, on a map accompanying the report, in the gen- 

 eral region of Silverton. 



In 1876 was published the eighth annual report of the Hayden survey -the 

 second one dealing particularly with the geology of Colorado. It contains reports 

 by Holmes, Hayden, Endlich, and Peale, all of which are considered in detail in 

 the geological discussion. S. G. Williams described the geology near Can^'on; 

 Powell's book upon the geology of the Uinta Mountains, with a paleontologic por- 

 tion by White, also appeared; and a series'of maps by Gilbert, Marvine, and Howell 

 were published the same year. 



In 1877 appeared the ninth annual report of the Hayden survej', containing 

 papers by Holmes, Endlich, Peale, and Hayden. These, so far as they concern the 

 subject in hand, are discussed in detail in the resume. The same year saw the publi- 



