"CERATOPS beds" OF WYOMING AND MONTANA 245 



palms, two of which are different from those recorded from the same 

 formation in Converse County. Brown describes the dinosaur-bear- 

 ing beds as resting on the marine Fox Hills. He says: 



In 1 90 1 I obtained characteristic fossils from both formations 

 near their contact at that locality (Alkali Creek). At that place the 

 conditions are similar to those in the Hell Creek region.'* 



This statement has been interpreted to mean that the "Ceratops 

 beds" there rest unconformably on the Fox Hills sandstone and that 

 the 400 feet of barren sandstones intervening between them in Con- 

 verse County have been removed by erosion. While this may be true 

 it is obviously unsafe to assume that it is the correct explanation until 

 it is definitely known that both the dinosaurs and the marine Fox Hills 

 invertebrates have the same vertical range, respectively, in both sec- 

 tions. It is possible that the Fox Hills invertebrates found on 

 Alkali Creek were in sandstones represented by the 400 feet of barren 

 sandstones farther south and it is likewise possible that some dinosaurs 

 were found in the same member. These localities are near the 

 southern boundary of the Newcastle quadrangle which has been 

 mapped and described by N. H. Darton.'^ His statements concern- 

 ing the formations in question are of interest in this connection: 



West of the wide valley in which the Pierre formation occurs there 

 rises a low escarpment due to a series of thin beds of hard sandstone 

 which belongs to the Fox Hills formation. There are two or three 

 thin layers of this sandstone, with shaly beds intercalated, and an 

 underlying series of soft, clayey sandstone having a thickness of only 

 50 feet. The basal members contain abundant distinctive fossils, 

 including at some places large numbers of Veniella. There is a con- 

 formable transition through 20 or 30 feet of sandy shales lying near the 

 base of the slope. Farther south, lower sandy beds of the formation 

 often contain large, fairly well-defined concretions due mainly to local 

 increase of lithification 



The breadth of the outcrop of the Fox Hills formation is not more 

 than a mile in most places and is often considerably less. South of 

 Robbers Roost Creek it widens to 5 miles. The thickness of the for- 

 mation is from 150 to perhaps 200 feet, increasing southward, but 

 gradually diminishing to the north to 75 feet, the decrease being largely 

 in the lower beds. There is some doubt as to the upper limit of the 



>' Bull. Am. Mus. Xat. Hist., Vol. XXIII, 1907, p. 845. 



»=^ Newcastle folio (No. 107), Geol. Atlas U. S., U. S. Geol. Survey, 1904. 



