542 E. RUSSELL LLOYD AND C. J. HARES 



the same horizon. One example is cited by Calvert^ where in 2 

 miles the somber beds transgress a distance of 200 feet upward 

 into the yellow. 



At present the only accepted criterion for the distinction of the 

 Lance formation from the Fort Union in areas where the Lebo 

 andesitic member of the Fort Union^ and the Cannonball marine 

 member of the Lance are absent is the presence in the former of 

 Triceratops and its associated fauna. On the basis of its fauna and 

 flora the Lance formation is approximately correlated with the 

 Denver and Arapahoe formations of the Denver Basin, Colorado,^ 

 and with a part of the "Upper Laramie" described by Veatch'' 

 in Carbon County, Wyoming. In both these regions the supposed 

 Lance equivalents usually rest unconformably upon a thick series 

 of fresh- and brackish- water beds — the Laramie of the Denver 

 Basin and the "Lower Laramie" of Carbon County, Wyoming. 

 Thus the correlations made on the basis of the vertebrate fauna 

 and the flora indicate that the Laramie is older than the Lance. 

 In the Denver Basin the Laramie rests conformably on the Fox Hills 

 sandstone. 



A comparison of the stratigraphic section in the Denver Basin 

 and adjoining regions with that in North and South Dakota pre- 

 sents certain anomalies which are not easy of interpretation. 

 Knowlton^ has maintained that there is an unconformity through- 

 out the northeastern Plains region between the Fox Hills sandstone 

 and the Lance which represents the time equivalent of the whole 

 of the Laramie of the Denver Basin as well as an unconformity 



' W. R. Calvert, "Geology of Certain Lignite Fields in Eastern Montana," 

 U.S. Geol. Survey Bull. 471, p. 197, 1912. 



= G. S. Rogers, "The Little Sheep Mountain Coal Field, Dawson, Custer, and 

 Rosebud Counties, Montana," U.S. Geol. Survey Bull. 531, pp. 168-172, 1913. 



3 S. F. Emmons, Whitman Cross, and G. H. Eldridge, "Geology of the Denver 

 Basin in Colorado," U.S. Geol. Survey Mon. 27, 1896. 



4 A. C. Veatch, "On the Origin and Definition of the Geologic Term 'Laramie,"' 

 Am. Jour. Sci., 4th ser., XXIV (1907), 18-22; Jour. Geol., XV (1907), 526-49. 



s F. H. Knowlton, "The Stratigraphic Relations and Paleontology of the 'Hell 

 Creek Beds,' 'Ceratops Beds,' and Equivalents, and Their Reference to the Fort 

 Union Formation," Washington Acad. Sci., Proc, XI (1909), 179-238; "Further 

 Data on the Stratigraphic Position of the Lance Formation ('Ceratops Beds')," 

 Jour. Geol., XIX (191 1), 358-76. 



