FOSSIL PLANTS AS AN AJD TO GEOLOGY. 375 



formations, are already important. Of these two or three 

 examples may be cited. 



The Post-Laramie beds of Middle Park, Colorado, have been 

 made the subject of an investigation by Mr. Whitman Cross. 

 After reviewing historically the opinions of various writers as to 

 the age of these beds, he discusses exhaustively the results of 

 recent work in this field. He reviews the fossil flora at length, 

 correcting many obvious errors of locality and horizon into 

 which the early collections had fallen, and finally presents a 

 revised list of the plants known certainly to have come from the 

 Middle Park beds. In the light of the revisions of the Laramie 

 and Denver floras, nearly 75 per cent, of the species enumerated 

 in this list are found to be common to the Denver beds. The 

 complete agreement of the paleobotanical with the other geol- 

 ogical evidences is well shown in conclusions of Mr. Cross, 

 which are as follows : " The unconformable relationships, lithol- 

 ogical constitution, and fossil flora all indicate the equivalence of 

 the Middle Park and Denver beds. No evidence seems to 

 indicate any other correlation."^ 



The Laramie and Post-Laramie beds of Montana have been 

 studied by Mr. W. H. Weed.^ His paper gives an account of a 

 series of beds heretofore embraced within the Laramie, and 

 covering the greater portion of the State of Montana east of the 

 Rocky Mountains. It is shown stratigraphically that the thick- 

 ness of some 13,000 feet of strata belong to three formations : 

 the Laramie, the overlying Livingston, and the higher Fort 

 Union beds. 



Fossil plants occur in all three of these formations, and from 

 their study it is made clear that the Livingston beds occupy the 

 same position in Montana, with reference to the Laramie, as do 

 the Denver beds in Colorado. Of 22 species of plants found in 

 the Livingston beds no less than 17 are found either exclusively 

 in the Denver, or have their greatest development in this 

 formation. 



'Proc. Colorado Scientific See, 1892, p. 26 of reprint. 

 "Bull. U. S. Geol. Survey, No. 105. 



