CEETACEOUS PLAINS OF COLOEADO. 59 



elevation. Although these sandstones form by no means an unbroken ridge, 

 they may bo traced without difficulty from Box Elder Creek far to the 

 southward of the Big Thompson. From the top of this low lidge, the Fox 

 Hill beds extend out upon the plains with considerable uniformity, falling 

 away gently from the main range, and presenting a nearly level monoto- 

 nous surface. Where best observed, they have in general a north and south 

 strike, agreeing approximately with the conformable sedimentary ridges, 

 which rest upon the Archsean body. Along the immediate base of the 

 range, they afford but little variety or interest in structural features, lying at 

 low angles, nowhere deeply cut by drainage-courses, with the surface planed 

 down, and generally covered by vegetation. 



Along the base of the Laramie Hills, the Fox Hill beds are buried 

 beneath the unconformable Tertiary strata, and first reach the surface just 

 below the boundary-line of Wyoming. Here the exposures are quite irreg- 

 ular, owing to the uneven erosion of the overlying beds and a somewhat 

 local disturbance of the strata; but south of where Box Elder Creek enters 

 the plains, the lower members of the series may be recognized. 



In the low sandstone ridge mentioned above, organic remains, charac- 

 teristic of the boundary between the Fort Pierre and Fox Hill divisions, 

 may be collected in many localities. They were especially abundant just 

 east of Park's Station, about a mile north of the Cache la Poudre, and 

 between 3 and 4 miles southeast of Laporte. From the latter locality 

 were collected numerous well-preserved specimens of the genus Inoceramus, 

 including Inoceramus Barrahini, associated with Ammonites. 



The Fox Hill beds east of the Colorado Range are characterized through- 

 out by great uniformity in texture and physical habit, and consist of a 

 coarse sandstone formation, showing only variations in color from reddish- 

 brown to reddish-yellow. They are usually massive, carrying hard, com- 

 pact beds, interstratified between layers of a more friable nature, which, in 

 the uppermost beds, offer exposures far less numerous than in the lower, and 

 have therefore been less searched for organic remains. We have at the top 

 of the series several hundred feet of strata, whose beds have furnished no 

 fossils; at least to our parties. The thickness of the Fox Hill strata is some- 



