142 ,/. B. Hatcher — Ceratops Beds of Wyoming. 



in previous Cretaceous periods, and sufficient to cause a reces- 

 sion of the salt waters at the close of the Fox Hills. During 

 the Laramie, this region was occupied hy fresh-waters or in 

 places by dry land. 



This period of elevation which brought about the close of 

 the marine Cretaceous is thought to have been followed by a 

 period of subsidence during the Laramie. For, since the beds 

 of the Laramie were evidently deposited in shallow waters, as 

 is abundantly shown by the great number of lignite seams 

 which they contain, and still further in the Ceratops beds, at 

 least, by the absence of continuity of strata, frequent cross- 

 bedding, etc., it is impossible to account for so great a thick- 

 ness of beds, all bearing evidence of having been deposited in 

 shallow waters, except on the theory of a subsidence going on 

 over the region during the period in which they were laid 

 down. This subsidence must have been so gradual that the 

 upbuilding by sedimentation at the bottom of the waters kept 

 pace with the subsidence ; any increase in the rate of the 

 latter increasing the depth of the waters, and a decrease in the 

 rate of subsidence causing a decrease in depth. The latter 

 would bring about a condition requisite for the deposition and 

 preservation of vegetable matter which would be transformed 

 later into lignites. 



The Ceratops beds are thought to afford evidence in them- 

 selves of having been deposited not in a great open lake, but 

 in a vast swamp, with occasional stretches of open waters, 

 the whole presenting an appearance similar to that which now 

 exists in the interior of the Everglades of Florida. This con- 

 dition would account for the frequent changes from one mate- 

 rial to another in the same horizon, before referred to. In 

 some places in the beds, these changes are quite frequent, 

 strata of sandstones and shales replacing one another in great 

 confusion. It would also explain the cross-bedding so often 

 seen in the sandstones of this region, in localities remote from 

 the present border of the beds, and hence far removed from 

 the shore of the ancient lake or swamp. This cross-bedding 

 could hardh 7 occur in off-shore deposits of a great fresh-water 

 lake of any considerable depth. 



The conditions that prevailed over this region during the 

 period in which the Ceratops beds were deposited were prob- 

 ably those of a great swamp with numerous small open bodies 

 of water connected by a network of water courses constantly 

 changing their channels. The intervening spaces were but 

 slightly elevated above water level or at times submerged. 

 The entire region where the waters were not too deep was 

 covered by an abundant vegetation, and inhabited by the huge 

 Dinosaurs (Triceratops, Torosaurus, Claasau?>us, etc.), as well 



