W. C? 1 oss — New Devonian Formation in Colorado. 251 



graphic point of view, the discovery of this distinct ichthyic 

 fauna leads to certain correlations and gives much desired in- 

 formation concerning the lower Paleozoic section of western 

 Colorado. 



The most evident correlation of the Elbert formation is with 

 the so-called "Parting Quartzite" of central Colorado, in which 

 Spurr found fish remains determined by Eastman as of Upper 

 Devoniau character, and related to certain forms from the 

 Elbert formation. 



The name "Parting Quartzite" was used by Emmons in the 

 Leadville monograph* for a quartzite formation 70 feet or less 

 in thickness, occurring below the "Blue Limestone" in which 

 Lower Carboniferous fossils had been found, and the "White 

 Limestone," supposed to be of Silurian age. The "Parting 

 Quartzite" was also provisionally assigned to the Silurian. 



At Aspen, on the northeastern flank of the Elk mountains, 

 Spurr f found the beds corresponding in stratigraphic position 

 to the Parting Quartzite of Leadville, to consist of alternating 

 dolomite, dolomitic shale, and quartzite, the last on the whole 

 subordinate, but the old name for the formation was retained. 

 From certain shaly beds at Aspen, Spurr and Tower obtained 

 the fish remains referred to by Dr. Eastman in the accompanying 

 paper. Upon the provisional determinations of this material 

 by ATalcott and Girty, the Devonian age of the "Parting 

 Quartzite" was advocated by Spurr. He also pointed out the 

 resemblance of the fish-bearing formation of Aspen to the beds 

 observed by Walcott \ in the lower Kanab valley of Arizona, 

 briefly stated to contain " placoganoid fishes of a Devonian 

 type." 



The stratigraphic equivalence of the Elbert formation of the 

 San Juan region with the "Parting Quartzite" is further sup- 

 ported by the correlation of the Ouray and Leadville (Blue) 

 limestones, rendered necessary by the studies of Grirty, who 

 shows that both possess an upper Devonian invertebrate fauna 

 in their lower portions and a Mississippian fauna in their up- 

 permost strata. The Carboniferous forms only were found at 

 Leadville, and the Devonian fauna was the first obtained from 

 the Ouray limestone. 



The correlation of the Elbert formation and the " Parting 

 Quartzite" with the strata of the Kanab valley, already sug- 

 gested by Spurr, is of special interest in view of the relations 

 of the Elbert fishes and the suggestions made by Eastman re- 

 garding the geographic connections of that fauna. Unfortu- 



*Mon. U. S. Geol. Survey, vol. XII, p. 61. 



f " Geology of the Aspen Mining District, Colorado," U. S. Geol. Survey, 

 Mon. XXXI, 1898, pp. 13-22. 



X This Journal (3), vol. xx, 1880, p. 224. 



