PAL.EOXTOLOGH'AL AND STRATIGRAPHICAL METHODS CONTRASTED. 280 



tinctly fresh-water and separated from the Laramie proper, or, as they desig- 

 nate it, "the lower Laramie," by a physical break; and this I have reason 

 to believe is the case in at least one locality where the vertebrate fauna, 

 which that of the Denver beds most resembles, has beenfouud. 



Conclusions — In no region can the palaeontologist afford to neglect the 

 evidence of stratigraphy and geological structure, and this is especially true 

 in a new and extremely complicated region like the Rocky Mountains, where 

 already the succession of life has been found in certain horizons to vary 

 quite markedly from the laws previously established by studies in Europe 

 and the east. The stratigrapher, on the other hand, must necessarily depend 

 on the palaeontologist for such determinations of the relative age of his 

 horizons as will enable him to establish correlations betweeu different series 

 of beds between which there may exist stratigraphical or geographical gaps 

 or hiatuses. 



For the accumulation of material essential for true and complete geologi- 

 cal history of a given region it is therefore necessary, not only that each 

 should freely furnish the other with all the facts he has determined from his 

 particular standpoint, but also that he should draw his conclusions, not from 

 that standpoint alone, but give due weight as well to the evidence afforded 

 from the standpoint of his collaborator. 



It is in pursuance of this idea that I have laid stress upon the importance 

 of the movement at the close of the coal-bearing Laramie in the Rocky 

 Mountain region ; and I desire to protest against what seems to be a tendency 

 among those who are studying the pakeontology of the region to give little 

 weight to it, or even to neglect it altogether in their determination of hori- 

 zons. It is unquestionably one of the most important events in the orograph- 

 ical history of the entire Cordilleran system. With the exception of the 

 great unconformity between the Archrean and all overlying sediments, 

 which is a phenomenon sui generis and altogether exceptional, no movement 

 has left such definite evidence as that which followed the deposition of the 

 coal-bearing rocks, to which the name Laramie has by universal consent 

 been applied. Against the positive testimony of nearly horizontal beds of 

 Eocene or later age actually overlapping the edges of more or less steeply 

 upturned Laramie beds, found iu so many and in so widely separated por- 

 tions of the region, the negative evidence of conformity of angle between 

 these beds in other localities has absolutely no weight at all. 



It is further a fact universally admitted that while the beds deposited pre- 

 vious to the Laramie were marine, all deposited since that period were essen- 

 tially fresh-water sediments. Now, it is kuown that land and fresh-water 

 molluscs are of little value as indices of the passage of geological time. Tt 

 seems reasonable, moreover, to assume that, iu a region where land surfaces 

 have existed throughout the orographic movements, fewer extinctions or 



