Report of the United States Geological Survey of the Territories Volume 8

Report of the United States Geological Survey of the Territories Volume 8

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This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1878 edition. Excerpt: of which, P. primrwa, represents, by leaves and scales of seeds, the only dicotyledonous plant found in the flora of Comes, a Greenland Lower Cretaceous flora, composed of seventy-five species of Filices, Selaginm, Cymdem, Convfera, and a few monocotyledonous, mostly of Jurassic or W'ealden types: this Populus is thus the oldest dicotyledonous plant known as yet. From this, we cannot be surprised to find the generic type already preponderant at a higher stage of the Cretaceous, that of the Dakota group, whose flora is composed mostly of dicotyledonous plants. No species of Populus, however, has been described to this time from the Cretaceous of Europe. This is a remarkable fact, rendered more striking by the scarcity of representatives of the same genus in the Eocene of that continent, which has ' until now only two species, both from the lower members of the formation, Sezanne and Belleu. Besides five Tertiary species described by Dr. Newberry from the Fort Union and Yellowstone Lignitic, and which may be Eocene, we have six others, positively referable to this formation, one of which is from Vancouver, two are common to the Mississippi and the Colorado Lignitic, and two have been obtained from the lowest Tertiary strata of Point of Rocks, which immediately rest upon the Cretaceous, and whose flora still preserves a few representatives of Cretaceous types. In the Miocene of Europe, however, the genus takes a large predominance, twenty-eight species being there described from this formation. To the present time, we have only ten; but considering the number of Tertiary species known from both continents, _, this indicates about the same proportion in the geological distribution. Seven of the American Miocene species are common...
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Product details

  • Paperback | 144 pages
  • 189 x 246 x 8mm | 268g
  • United States
  • English
  • black & white illustrations
  • 1236990102
  • 9781236990105