192 KNOWLTON 



4. CUSTER, MONTANA, AND VICINITY. 



Beyond the point indicated above the conditions to the west and 

 southwest of Forsyth are not definitely known, though the marine 

 Cretaceous extends westward nearly to Myers; but from observa- 

 tions made from a train, it seems not improbable that the "somber 

 beds" may be traced as far as Bighorn or Custer. In any event, 

 beds known to be of this age were observed near the latter place by 

 Mr. L. J. Pepperberg, of the United States Geological Survey, dur- 

 ing the past season. The section, there several hundred feet in 

 thickness and resting on one of the upper members of the Pierre, is 

 made up of light colored sandstones and shales. At a point near the 

 top of the exposed section the following small collection of plants 

 was secured: 



Four and one-half miles southeast of Bighorn, Montana. 

 Platanus nohilis Newb. 

 Popiilus cuneata Newb. 

 Sapindus sp. 



5. BULL MOUNTAIN, MONTANA, AREA. 



The so-called Bull Mountain coal field" of Montana covers an 

 area of about 750 square miles, lying mainly to the south of the Mus- 

 selshell River and some 20 miles north of the Yellowstone River. 

 On the southeast the lower member of the Fort Union presumably 

 connects more or less closely with the area just mentioned near 

 Custer, while to the northeast it will probably be found to extend 

 directly into the Hell Creek area. The beds in question, which are 

 composed of usually light colored sandstones, clays and carbonaceous 

 shales, are about 2000 feet in thickness and rest upon Pierre shale. 

 They have usually been referred on stratigraphic grounds to the 

 Laramie, but there is little question of their belonging to the lower 

 Fort Union, though plants have not thus far been reported from 

 them. 



6. MELVILLE, MONTANA, AREA. 



The area now to be considered lies cast of the Crazy Mountains 

 and about 25 miles north of Big Timber. The geological structure 



" See Woolsey, Bull. U. S. Geol. Surv., 341 A, 1908, p. 60. 



