W. Cross — Post-Laramie Deposits of Colorado. 35 



In attempting to correlate the new formations of the Denver 

 field by means of their vertebrate fossils it is necessary to 

 know the horizon or horizons which have furnished the large 

 new fauna recently described. A review of the papers published 

 by Prof. Marsh shows, however, that except for fossils which 

 came from the Denver region no detailed evidence is given as 

 to the stratigraphical or geographical position of beds contain- 

 ing any of the fossils described. There are only the general 

 statements that they " come from the typical Laramie of 

 Wyoming" or "of Montana." All localities are correlated as 

 belonging to one general horizon, " the Ceratops beds," and 

 the assertion is made that : " This horizon is as strongly 

 marked as that of the Atlantosaurus beds, and has now been 

 traced for nearly eight hundred miles along the eastern base of 

 the Rocky Mountains." And as to stratigraphical relation to 

 lower beds, "Toward the north, it is underlaid by marine 

 Cretaceous strata containing Fox Hill fossils, but farther south, 

 various older formations are found immediately beneath it." * 

 It certainly seems natural and it may almost be said probable 

 that such a new and specialized group of animals should char- 

 acterize a well marked geological horizon. But as far as the 

 actual position of the Ceratops beds has been described, 

 namely, in the Denver region, they are separated from the 

 normal Laramie by a great unconformity, and it remains to be 

 demonstrated that the new forms occur at all in the Laramie 

 proper. It is believed to be a fact that in all the great Lara- 

 mie formation of Colorado, where it has been studied more 

 thoroughly and connectedly than anywhere else, no represent- 

 atives of the Ceratopsidse have been found ; and that the same 

 is true of the adjacent connected deposits in New Mexico and 

 Utah. None of the species described by Prof. Marsh has been 

 stated to come from the Laramie coal-measures of southern 

 "Wyoming, but it seems probable that the historic Dinosaur 

 called Agathaumas by Cope, the discovery of which at Black 

 Butte in 1872 played such an important part in deciding opin- 

 ion as to the Cretaceous age of the Laramie, may prove to be 

 of importance in the present discussion also. It is now 

 thought by both Cope f and Marsh % that this form is a horned 

 Dinosaur. If this is true the Ceratopsidse are represented to 

 the west of the Front range in what have been called typical 

 Laramie strata by some authors. But it happens that the 

 Black Butte locality is one concerning which geologists have 

 differed, considerably in their observations and opinions. A 



*This Journal, vol. xlii, p. 338, 1891. 



fAmer. Naturalist, xxiii, p. 715, 1889. % This Journal, xliii, p. 83, 1892. 



