Haynes: Fauna of the Upper Devonian in Montana. 23 



a section measured by him in southwestern Wyoming, on Labarge 

 Mountain, northeast of the town of Viola. Here he notes the presence 

 of 80 feet of drab shales and shaly, thin-bedded magnesian and siliceous 

 limestone, barren of fossils, occurring below dark gray Madison lime- 

 stone and above the Jefferson limestone. 



The southernmost occurrence of the Three Forks Formation, which 

 the writer has seen recorded, is in a section near Bear Lake in northern 

 Utah in the Randolph quadrangle. Mr. Richardson^ reports the 

 presence of 200 feet of soft reddish shaly limestone, which is poorly 

 exposed, occurring between the Jefferson and Madison limestones. He 

 considers this the equivalent of the Three Forks Formation farther 

 north. 



North of the Yellowstone Park the Three Forks Formation has been 

 recognized in the Livingstone, Little Belt Mts., and Fort Benton Quad- 

 rangles. In the Livingstone quadrangle^ it is described as a series of 

 thinly bedded, impure limestones, alternating with thin beds of shale, 

 with a total thickness of about 250 feet. The top beds are often purple 

 and red in color. The lower strata are earthy shales in beds a few 

 feet thick, alternating with limestone layers of equal thickness. 



In the Little Belt Mountains Quadrangle^ the upper member of the 

 Monarch formation is equivalent to the Three Forks formation of 

 other quadrangles. It consists of thinly bedded shaly limestones 

 (with much argillaceous matter), of a bluish gray color when fresh, but 

 weathering to a straw-yellow or pink color. The thickness is usually 

 40 or 50 feet and does not exceed 140 feet. 



In the Fort Benton quadrangle^" the upper 30 feet of the Monarch 

 Formation is equivalent to the Three Forks Formation, and consists of 

 reddish shaly limestone with abundant Devonian fossils. This is as 

 far north as the Three Forks Formation has been recognized so far as 

 the writer can ascertain. 



Northwest of Three Forks the Formation has been recognized in the 

 Helena District by Dr. Knopf" who describes the section as follows: 



Fine-grained black carbonaceous shales 15 feet. 



Light-colored fossiliferous calcareous shales, grading downward 



into earthy shales with interbedded quartzite 270 feet. 



Total 285 feet. 



7 Richardson, G. B.. Amer. Jour. Set., Ser. IV, Vol. XXXVI, pp. 406-416, 1913. 



8 Atlas Folio. U. S. G. S., No. i. 



9 Atlas Folio, U. S. G. S., No. 56. 

 1" Atlas Folio, U. S. G. S.. No. 55. 



11 Knopf, A, Bull. U. S. G. S., No. 527, p. 92, 1914. 



