IF. Gross — Post-Lararaie Deposits of Colorado. 33 



and all overlying sediments, ... 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 univer- 

 sal consent been applied."* And while Mr. Hills thinks that 

 some of the effects hitherto ascribed to the post 7 Laramie 

 movement belong to that following the Bridger Eocene, his 

 conclusion in regard to the Arapahoe, Denver and equivalent 

 beds, is as follows : " From all the evidence available it appears 

 that stratigraphically these beds are not Laramie, since to refer 

 them to the Cretaceous would bring us face to face with the 

 necessity of conceding an earlier date than post-Cretaceous to 

 the Rocky Mountain revolution. Nor are they, paleontologi- 

 cally, a part of the recognized Eocene. Whence we must con- 

 clude that they are not assignable to either of these terranes,, 

 but should be regarded as transition beds deposited subsequent 

 to the beginning of the post-Cretaceous movement, or probably 

 during its progress and hence of post-Laramie age."f 



The Denver beds contain a very large and well preserved 

 fossil flora. So do the coal-measures of the Laramie in the 

 same field, and more than 160 species have been described 

 from this district by Lesquereux.;}: It has already been 

 shown§ in describing the Denver beds that from the statements 

 of this author only a very small percentage of the described 

 species can be definitely assigned to one of the two plant- 

 bearing horizons, nor is the desired information to be found on 

 the labels or in the catalogue of the National Museum where 

 the original specimens are now deposited. Examination has 

 also shown a lamentable inaccuracy in designation of localities 

 for the fossil plants of various other localities assigned to the 

 Laramie. This is true especially of the plants from the Mid- 

 dle Park beds, as has been mentioned. The existing confusion 

 is so great that no credible table can now be constructed from 

 published data to show, excepting in a most general way, 

 whether there is or is not a noteworthy difference between the 

 known flora of the Denver and Middle Park beds and that of 

 the Laramie proper. But on the basis of new and extensive 

 collections ~from known horizons a thorough revision of this 

 portion of the Laramie flora is now in progress in the paleo- 

 botanical department of the Geological Survey. Until the 

 results of this revision can be made public a discussion of the 



* Orographic movements in the Rocky Mountains, Bull. G-. S. A., I, p. 285, 1890. 



f Orographic and structural features of Rocky Mountain geology, Proc. Colo. 

 Sci. Soc , vol. iii, Part III, p. H97. 



% Monographs of the Hayden Survey: vol. vii, "The Tertiary Flora;" vol. 

 viii, "The Cretaceous and Tertiary Floras;" also, Bull. Mus. Comp. Zool , Har- 

 vard College, vol. xvi, No. 3, 1888. 



§ This Journal, vol. xxxvii, p. 272, 1889. 



Am. Jour. Sci.— Thihd Series, Vol. XLIV, No. 259.— July, 1892. 

 3 



