"CERATOPS beds" OF WYOMING AND MONTANA 261 



The Unios indicate close relationship with the fauna of the " Cera- 

 tops beds" of Hell Creek and Converse County. 



Stone describes the upward stratigraphic succession as follows: 



Taken as a whole, the upper part of the Laramie formation is 

 distinguished from the formations above and below by its light-gray 

 color in comparison with their somber hues. It is composed largely 

 of soft gray sandstone and variegated shale. The gray beds, from 

 1000 to 2400 feet thick, make a conspicuous valley across the middle 

 of T. 6 N., Rs. 13 to 16 E. As a whole the formation weathers so 

 readily that it normally forms low country, and for some miles in 

 this area it coincides with the valley of Fish Creek. The gray beds 

 of the Laramie formation are overlain, possibly with unconformity, 

 by somber-colored sandstone and shale which may represent the 

 Livingston formation. Sufficient paleontologic evidence has not been 

 obtained, however,to determine the limits of these stratigraphic units. 

 A section measured by C. A. Fisher and T. W. Stanton on a fork of 

 Big Elk Creek gives a thickness of 5592 feet from the base of the 

 Laramie to the base of the sandstone and grit of probable Fort Union 

 age, and of 10,324 feet for the beds above the Bearpaw shale. Further 

 field work is necessary before the lithologic and paleontologic dis- 

 tinctions of the Laramie and Livingston formations can be deter- 

 mined. 



The Fort Union formation, of unknown thickness, but exceeding 

 4,300 feet, is the youngest in this area. It is composed largely of 

 sandstone, alternating with shale. The base of the formation is a 

 particularly massive, coarse-grained sandstone which forms pro- 

 nounced wooded ridges. Fort Union beds underlie the southern 

 part of T. 6 N., Rs. 12 to 16 E., and compose the north and east 

 bases, at least, of the Crazy Mountains. 



It was my privilege in 1908 under the guidance of Mr. A. C. Silber- 

 ling to review the upper part of the Fish Creek section, from the Tri- 

 ceratops horizon upward, especially in townships 5 and 6 north, ranges 

 15 and 16 E. The area is important because it was here that Douglass^^ 

 found the first specimens of the primitive mammalian fauna on which 

 the correlation of the Fort Union with the Puerco and Torrejon for- 

 mations is based, and with one exception all the "Fort Union" mam- 

 mals known were found within a few miles of this place. The strati- 



32 Proc. Am. Philos. Soc, Vol. XLI, 1902, pp. 217-224. Annals Carnegie 

 Mus., Vol. V, 1908, pp. 11-26. 



