EECAPITULATION OF PALEOZOIC FORMATIONS. 209 



brachiopod fades and is quite different from the fauna of the upper Maroon as 

 exemplified by the Rico formation. It is, in fact, more like the fauna of the lower 

 Mai-oon, but at the same time contains many novelties. No satisfactory estimate of 

 this evidence can be made pending a careful study of the Weber fauna, which I hope 

 to make at some future time. If the differences prove to be as important as they 

 at first appear, the paleontolog'io correlation of the Maroon and Weber sei'ies would 

 hardly be justified. It is possible to suppose that the Mai'oon series is absent in Utah, 

 or that it, combined with the Weber limestone, is represented by the upper portion 

 of the Wasatch limestone and that its horizon is below the AVeber quartzite. In 

 that event the simultaneous occurrence of these two series in the Uinta Mountains 

 would adequately- account for the Uinta sandstone, even if it became necessarj' to 

 refer to the Carboniferous the whole of that ^reat series. On the other hand, a 

 provincial influence may possibly be cited to account for the faunal peculiarities 

 noted above and others corresponding to them. It is necessarj' to consider that the 

 waters of the Mississippian sea extended into Utah and possibl}' as far west as the 

 Sierra Nevada, but in the elevation which preceded the first Pennsylvanian sediments 

 this area must have been analyzed into a more composite geography. The Pennsyl- 

 vanian faunas of Colorado have ever}' appearance of being provincially related to 

 those of the Mississippi Valley. The faunas of Pennsvlvanian age found to the 

 west and southwest, however, are sufficiently different and novel to suggest that the 

 post-Mississippian elevation, if it did not establish a barrier between the Colorado 

 and Utah seas, at least aroused influences sufficiently potent to modify the faunas of 

 the two areas. 



I shall permit mj^self , befoi'e closing, a few words upon the nomenclature of the 

 Carboniferous formations of Colorado, deprecating not so much that many names 

 have been emploved, but that some ha\'e been used in several senses and some have 

 been imported from such a distance that the correlation intimated unist have been 

 originally doubtful and is now perhaps more than doubtful. 



Of Mississippian age we have the Leadville limestone of central Colorado, the 

 Millsap limestone of the Front Range, and the Ouray limestone of southwestern 

 Colorado. While 1 believe that the Leadville, Millsap, and Ouray limestones, so 

 far as their Mississippian faunas are concerned, and for that matter the Red Wall, 

 Wasatch," and Madison limestones, can be correlated, the employment for them of 

 distinct formational names seems to be a field matter of geologic propriety and to 

 be judged onlj' from that point of view. I think, however, that it would have been 

 better, in view of the fact that the Leadville and Ouray limestones contain a fauna 

 of Devonian as well as one of Mississippian age, if two formations, instead of one, 



al mean only the lower or Mississippian portion of the Red Wall and Wasatch limestones and only the Red Wall 

 limestone of the Grand Canyon. 



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