Page:The Journal of geology (IA journalofgeology21894univers).pdf/391

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 geological evidences is well shown in conclusions of Mr. Cross, which are as follows: "The unconformable relationships, lithological constitution, and fossil flora all indicate the equivalence of the Middle Park and Denver beds. No evidence seems to indicate any other correlation."^[1]

The Laramie and Post-Laramie beds of Montana have been studied by Mr. W. H. Weed.^[2] 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 thickness 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.