24 Annals of the Carnegie Museum. 



Another section is as follows: 



Black shale 56 feet. 



Calcareous argillite 136 " 



Shale 40 " 



Total 232 feet. 



Farther west, in the Philipsburg Quadrangle,'^ the Three Forks 

 Formation is apparently absent, and the Jefferson limestone is immedi- 

 ately overlain by the Madison limestone. In the Camp Creek section 

 near Melrose, about 50 miles southwest of Three Forks, Dr. Kindle'^ 

 maintains that the Three Forks Formation is represented by a bluish 

 gray argillaceous shale and huffish shale in the lower part, with 

 limestone bands near the middle, having a total thickness of about 

 200 feet. 



The boundaries of the region throughout which the Three Forks 

 Formation has been recognized may tentatively be placed at latitudes 

 48° and 42° north and longitudes 109° and 113° west. This includes a 

 region with a north-south dimension of about 400 miles and an east- 

 west dimension of 200 miles. It is very evident from these figures 

 that the Three Forks Formation has not nearly so widespread a dis- 

 tribution as the Jefferson limestone, which underlies it, or the Madison 

 limestone, which overlies it. 



Although the Three Forks Formation has not been recognized by its 

 lithological characters outside of the region just noted, it is likely from 

 faunal evidence that the sea, in which the Three Forks Formation was 

 deposited, covered an area much greater than that in which the for- 

 mation has been recognized. The similarity of some of the fauna of 

 the lower part of the Ouray limestone of Colorado with the brachiopod 

 fauna of the Three Forks Formation indicates a connection in that 

 direction, and the presence of a small Ouray faunule from the beds 

 transitional from the Lower Banff limestone to the Lower Banff shale, 

 reported by Dr. Shimer'^ in the Lake Minnewanka section in Alberta 

 indicates a spreading of this Upper Devonian sea to the north. 



The Fauna of the Three Forks Formation. 

 The writer has made a careful study of the collection of fossils made 

 by Dr. Raymond for the Carnegie Museum and also of his own col- 



12 Calkins, F. C, Prof. Pap. U. S. G. S., No. 78, p. 65, 1913. 



" Kindle, E. M., Bull. Avter. Pal., No. 20. p. 9, 1908. 



i^Shimer, H. W.. Bull. Geol. Soc. Afn., Vol. XXIV, pp. 233-240, 1913. 



