CARBON BASIN. 147 



characteristic of a much, lower horizon ; among them, a Smilax grandifolia, 

 Bhamnus Goldianus, Cinnamomum Mississippiense, and Ficus tilicE folia. 



At the time of our visit to this district, we made diligent search for 

 Molluscan remains, but without success, and, so far as known to us, no ver- 

 tebrate or invertebrate forms have as yet been found in the Carbon Basin, 

 with the exception of a single imperfect and distorted specimen of a Vivipa- 

 rus, having no specific character. 



The evidence as to the age of these deposits rests either upon the fossil 

 plants which they contain, or upon their stratigraphical position, and, where 

 such testimony disagrees, it would seem that the latter must necessarily 

 receive the greater weight. This is especially the case where so much 

 doubt has already been raised in other localities of the Rocky Mountains 

 as to the importance of plant evidence in determining geological horizons 

 between Cretaceous and Tertiary beds. 



Professor Lesquereux, notwithstanding he feels so positive as to the 

 Miocene age of the Carbon beds, does not hesitate to place them below the 

 Green River series, giving them a position, in relation to the latter horizon, 

 which few geologists will be disposed to dispute, and which the geological 

 maps and sections accompanying this report conclusively prove. In the 

 second chapter of this volume, it will be shown that the Green River beds 

 are undoubtedly of Eocene age ; that they are, moreover, overlaid by several 

 thousand feet of Eocene deposits, and underlaid by a heavy thickness of 

 the Vermillion Creek series, also Eocene ; and that the latter overlies uncon- 

 formably beds occupying the same horizon as the Carbon formation, which 

 we regard as of Upper Cretaceous age. 



West of Simpson Ridge, the Fox Hill sandstones pass under the Laramie 

 beds, and the latter extend westward as far as Saint Mary's Peak, a dis- 

 tance of 15 miles, where they are again limited by the coming to the surface 

 of the underlying sandstones. North of the railroad, the Laramie formation 

 stretches beyond the boundary of our map, and its limits in that direction 

 have never been determined; while, to the southward, it is hemmed in by 

 outlying ridges of Fox Hill sandstone connected with the Elk Mountain 

 upheaval. The rocks of the Laramie division are chiefly loose, friable sand- 

 stones, of rusty-yellow and reddish-brown colors, and in places carrying 



