XLVIII 



INTRODUCTORY REM AUKS. 



souri in Montana Territory. But we have reason mow to believe that it 

 exists at other localities in the Upper Missouri country, either under the 

 Fort Union group, or at some other places where the latter may not exist. 

 At the typical locality, it evidently rests upon well-marked Cretaceous strata 

 belonging to the horizon of the upper part of the Fox Hills group; and 

 both have been upheaved together in such a manner as to show conclusively 

 that there is no discordance of stratification, or, in other words, that they 

 are conformable.* Owing to this disturbed condition of the strata, it was 

 found difficult to make out a detailed section showing the order of succession 

 of the whole series ; but the following, prepared from Dr. Hayden's notes, 

 and the study of the fossils from these beds, will at least convey a general 

 idea of their nature here, if not of the details of the whole group. It is 

 given in descending order. 



Section of the Judith Hirer group as seen at the mouth of Judith River. 



* The occurrence here together of these two entirely distinct formations, has caused some little 

 confusion in citations of what has been written about theni. For instance, remarkB uiade by the author 

 in regard to the undoubted Cretaceous beds here, in a little report on fossils from the same horizon 

 near Greeley, Colorado (Bull. U. S. Geol. Survey, No. 1, 2d ser., 40 and 41), have been, by an oversight, 

 quoted by my young tiieud Dr. Peale, as if intended to apply to the brackisb-water Judith River 

 group, here under consideration, instead of to the well-marked Cretaceous beds there. (See Dr. Hay- 

 den's Ann. Report U. S. Geol. Survey of the Territories, first division, l^Tii. 1 15.) 



