WARU] HISTORICAL REVIEW OF OPINION. 421 



lent of the Bitter Creek series in Wyoming. As to the Fort Union beds, 

 he adheres to his former opinion, that they represent the lower Eocene. 

 He deprecates the attempt to unify all the lignite-bearing rocks, and 

 remarks: "The presence or absence of lignite proves nothing of itself, 

 as lignite undoubtedly occurs in both Cretaceous and Tertiary rocks in 

 the far West." In his comparisons of the Fort Union with the Wyoming 

 deposits he states that the species of the former are all different from 

 those of the Bitter Creek group, and concludes that these groups at 

 least cannot be equivalents. Mr. Meek's concluding remarks upon the 

 contiicting testimony of fossils and its lessons (pp. Ix, Ixi) are a model 

 of scieutitic reasoning, and doubtless went far to mitigate the acerbity 

 of this prolonged debate. 



Powell's Geology of the Uintah Mountains was published the same 

 year (187G) as the report last mentioned, and contains an important con- 

 tribution to the present subject. Professor Powell and Dr. C. A. White 

 had gone carefully over the disputed ground of the Bitter Creek dis- 

 trict, tracing it up to its junction with the Washakie and Green River 

 beds on the west, and in this volume both these authorities record their 

 conclusions, which are in substantial accord. The former remarks (p. 

 67): "The relation of these groups to those established by Professors 

 Meek and Hayden on the Upper Missouri is not well determined. * * * 

 All the evidence that has been published by Dr. Hayden and members 

 of his corps concerning the Park Province, and all my own observations 

 in that region, lead me to the conclusion that a long chain of islands 

 stretched in a northerly and southerly direction through that region of 

 country, separating the Cretaceous sea of the Plateau Province from 

 the Cretaceous sea of the Upper Missouri." 



Between Black Buttes Station and Point of Eocks Station, on the 

 Union Pacific Railroad, these gentlemen discovered a "physical break" 

 in the series, exposing at the latter point a lower formation; and at this 

 point they fixed the line between Mesozoic and Cenozoic strata, assign- 

 ing, in the table of groups on page 40, the Point of Rocks group to the 

 Cretaceous and the Bitter Creek group to the Tertiary. On this subject 

 Professor Powell says (p. 71): "On account of the discussions which 

 have arisen concerning the age of certain beds of lignitic coal, the plane 

 of demarkation between the Cenozoic and Mesozoic may subject me to 

 criticism; but, geologically, the plane is important, as it represents a 

 decided physical change, and it certainly harmonizes with the opinion 

 of paleontologists to a degree that is somewhat surprising. All of the 

 plants described by Professor Lesquereux and collected by himself and 

 others within this province have been referred by him to divisions in the 

 Tertiary, and are found in strata above this physical break, and hence 

 1 agree with him in considering them Tertiary. » * * The conclusions 

 reached from a study of the vertebrate paleontology by Professors 

 Leidy, Marsh, and Cope entirely harmonize with this division of the 

 Cenozoic and Mesozoic. There is a single exception to this: Professor 



