PALEOZOIC STRATIGRAPHY OF ROCKY MOUNTAINS 253 



Peak quartzite 1 and the quartzite at Geneva 2 include no species, 

 and only two genera (Orthis and Endoceras) in common with the 

 published lists of fossils from the Harding sandstone 3 and the basal 

 Bighorn sandstone. 4 



THE MIDDLE AND UPPER ORDOVICIAN DOLOMITES 



Extent of the Bighorn dolomite. — -The Bighorn dolomite was 

 named by Darton 5 from its characteristic exposures on both flanks 

 of the Bighorn Range in northern Wyoming, and by him was cor- 

 related with the White wood limestone of the Black Hills and with 

 the Fremont limestone of the Front Range of Colorado. 6 The same 

 author later recognized the Bighorn dolomite in the Owl Creek 7 and 

 Wind River 8 ranges of Wyoming. Fisher 9 briefly described its 

 occurrence in Cedar and Rattlesnake Mountains, west of Cody, 

 Wyoming. Blackwelder 10 has identified it in the Gros Ventre and 

 Teton ranges, farther west. 



The Bighorn dolomite in Montana.- — -Both Darton" and Fisher 12 

 prophesied that the Bighorn dolomite would be found to be included 

 in the "Jefferson limestone" of Hague, and the truth of this 



I Richardson, op. cit., p. 410. 2 Blackwelder, op. cit. (1910), p. 527. 



3 N. H. Darton, "Fish Remains in Ordovician Rocks in the Bighorn Mountains, 

 Wyoming, with a Resume of the Ordovician Geology of the Northwest," Bull. 

 Geol. Soc. Amer., XVII (1905), 563. 



4 Ibid., pp. 554-56, footnote. 



5 N. H. Darton, "Comparison of the Stratigraphy of the Black Hills, Bighorn 

 Mountains, and Rocky Mountain Front Range," Bull. Geol. Soc. Amer., XV (1904), 

 379-448. 



6 N. H. Darton, "Description of the Bald Mountain and Dayton Quadrangles," 

 Geol. Atlas U.S., Folio 141 (1906), p. 4. 



'N. H. Darton, "Geology of the Owl Creek Mountains," Fifty-ninth Congress, 

 1st session, Senate Document No. 219 (1906), p. 15. 



8 N. H. Darton, "The Paleozoic and Mesozoic of Central Wyoming," Bull. Geol. 

 Soc. Amer., XIX (1908), 403-74. 



9 C. A. Fisher, "Geology and Water Resources of the Bighorn Basin, Wyoming," 

 U.S. Geol. Survey, Prof. Paper 53 (1908), p. 12. 



10 Eliot Blackwelder, unpublished manuscripts, U.S. Geol. Survey. 



II N. H. Darton, "Fish Remains in Ordovician Rocks in the Bighorn Mountains, 

 Wyoming, with a Resume of the Ordovician Geology of the Northwest," Bull. Geol. 

 Soc. Amer., XVII (1905), 554. 



12 Op. cit. 



