372 F. H. KNOWLTON 



stratigraphy of the area was, according to Stanton, 1 "the discovery 

 that the marine Fox Hills deposits extend about 400 feet higher 

 than had previously been determined, and that non-marine coal- 

 forming conditions were temporarily inaugurated here before the 

 close of Fox Hills time." If Hatcher's estimate of the thick- 

 ness of the beds assigned by him to the Fox Hills was anywhere 

 near correct this " discovery" would seem to increase the total 

 thickness to about 900 feet, yet nowhere in the paper mentioned 

 is a thickness greater than 400 or 500 feet claimed for it. This 

 appears difficult to explain unless the lower as well as the upper 

 limit of the formation has been changed. 



A number of sections are given by Dr. Stanton, in one of which 

 at least, namely that on Buck Creek, the top of the Fox Hills 

 appears to have been fixed by the presence of the plant Halymenites 

 major. The thickness of the Fox Hills in this section is given as 

 505 feet, though the highest horizon at which marine Fox Hills 

 invertebrates occur is about 180 feet below the top. 



In the section made on the divide between Lance and Buck 

 Creeks the Fox Hills is said to have a thickness of 445 feet, though 

 the lower member of the section only (30 feet above the Pierre 

 shale) is indicated as containing a Fox Hills fauna. 



The section made on the south side of the Cheyenne River at 

 the mouth of Lance Creek shows a thickness of 405 feet of Fox 

 Hills above the Pierre, but the highest point in the section at which 

 marine Fox Hills invertebrates were found is over 100 feet below 

 the top. It further appears from this section that the upper four 

 members, aggregating 115 feet in thickness, contain carbonaceous 

 and lignitic shales as well as fragments of dinosaur bone and 

 brackish-water invertebrates, certain of which are the same as those 

 found in, and there said to indicate the Laramie age of, the 400 

 feet of beds already mentioned as reported by Stanton and Knowl- 

 ton above the typical marine Fox Hills. 2 To the writer it seems 

 altogether more probable that the four upper members of this 

 section belong to the Lance formation and not to the Fox Hills, 

 and it appears that this was the view at first entertained by Dr. 



1 Am. Jour. Sri., XXX (1910), 184. 



2 Bull. Geol. Soc. Am., VIII (1897), 130. 



