CERATOPSIA LOCALITIES. 



175 



have examined them have believed, but they constitute a distinct horizon within the Montana group, which we have called 

 the Claggett formation, from old Fort Claggett, at the mouth of the Judith River, near which they are well developed. 



4. The Eagle formation, from its stratigraphic position and faunal relations, marks the base of the Montana group in this 

 region. 



5. The Bearpaw shales, the Judith River beds, the Claggett, and the Eagle formations all belong to the Montana group, 

 and together probably form the equivalent of the Pierre, as that term is generally understood, though the possibility is recog- 

 nized that in the typical area the Pierre may have more restricted limits. 



The following correlations are shown:" 



Sections in South Dakota, Montana, and Assiniboia. 



The Montana and Colorado groups are generally recognized as larger subdivisions of the strata lying between the Dakota 

 and the Laramie. The South Dakota and Nebraska section is the Meek and Hayden section with the Laramie added, while 

 the other two columns represent the sections studied by us [Stanton and Hatcher]. The queries in the lower part of the 

 columns indicate formations not seen by us, and the queries in the upper part of the columns indicate our doubts as to the 

 •correlation of any particular horizon in these sections with the Fox Hills and as to the limits of the Laramie and its 

 relationship with overlying formations that have been described in this region. 



DOG CREEK. 



The first Judith River locality mentioned by Stanton and Hatcher is at Dog Creek, a small 

 stream emptying into the Missouri from the south, about 2 miles below the mouth of Judith 

 River. This creek rises in the Moccasin Mountains and flows for 25 or 30. miles northward, first 

 in a narrow and shallow valley, through grass-covered table-lands, and for the last 12 or 15 

 miles through a deep, rugged canyon, with wild, deeply dissected badlands on either side. 



The walls of the upper valley are composed of Judith River sandstones and shales; those 

 of the deeper lower canyon are mainly the light ash-colored sandstones and darker shales and 

 clays of the Judith River beds above and "the darker buff-colored sandstones and dark sandy 

 or black clay shales of the underlying Claggett formation" below. 



For 5 to 8 miles from the mouth of Dog Creek the beds in the bluffs of the stream are 

 undisturbed, and in this stretch the Claggett underlies 300 or 400 feet of Judith River formation. 



A little farther up Dog Creek, in undisturbed areas, the Claggett formation disappears beneath the bed of the stream, 

 and the bluffs of the canyon are formed entirely of the Judith River beds, which have a maximum thickness here of perhaps 

 500 feet and are composed below of alternating layers of light, ash-colored sandstones and darker shales, abounding in numerous 

 fresh-water Mollusca.S 



a Loc. cit., p. 63. 



b Stanton and Hatcher, op. cit., pp. 37-38. 



