THE CARBONIFEROUS FORMATIONS AND FAUNAS OF 



COLORADO. 



Bj^ George H. Gikty. 



INTRODUCTION. 



In the following pages the geology and paleontology of the Carboniferous rocks 

 of Colorado are discussed from the viewpoint of the stratigraphic paleontologist. 

 This viewpoint is also that of one not personally acquainted with the field in question, 

 except in very small measure. I made or assisted in making a few collections of 

 fossils, and enjoyed the privilege of being- connected for a month with a field party 

 under the charge of Mr. Whitman Cross during the season of 1900. Most of the 

 extensive collections which I have studied are the work of others, and the strata, in 

 their characters and mutual attitudes, have been viewed only through the pages of 

 geologic reports. The tendencies of my work are almost exclusively toward the 

 historical geology, for from the nature of the case, even had I wished, it would have 

 been difiicult to deal with the structural or economic phases of the subject. 



The paleontologic data for this work reside in a rather extensive collection from 

 200 localities, representing the available resources of the Geological Survey and the 

 National Museum in the matter of Colorado Carboniferous fossils. In the paleonto- 

 logic discussion the purpose has been not so much to see what or how many species 

 occurred within the limits of Colorado as to ascertain their grouping into local and 

 formational faunas, and to determine, if possible, by means of the invertebrate fossils, 

 the relation to one another of the strata forming the different more or less discon- 

 nected and isolated areas of Carboniferous outcrop. Aside from such correlative 

 indications as the study of these collections has furnished, a fact of some interest, 

 though by no means for the first time brought to notice, is the close relation which 

 evidently existed in Carboniferous time between the Coloi'ado seas and those of the 

 Mississippi Vallej'. Almost the entirety of the numerous fauna recognized in 

 Colorado occurs also in the coal fields of the Ohio and Mississippi valleys, and it has 

 l)ecn found necessary to describe but very few species as new. 



