FLORA OF THE LARAMIE GROUP. 



The age of the Laramie Group of Hayden is not yet definitively deter- 

 mined. The remains of fossil plants, ahundantly procured from this 

 formation, especially at Golden, Black Buttes, and Point of Rocks, have 

 been recognized by botanists as pertaining to a flora mostly composed of 

 Tertiary types, while, according to zoologists, the fauna of the same for- 

 mation is Cretaceous in character. Though the question has already been 

 discussed at length and considered under diverse points of view, my own 

 opinion being given in the preceding volume of the •"U. S. Geol. Rep.." vii, 

 pp. 338-352, iu F. V. Hayden's "Ann. Rep.,'" 1872 to 74, etc., it is proper 

 briefly to present here some new facts bearing on the subject, and lo note 

 the conclusions which may be derived from them. 



1st. The flora of the Laramie Group has a relation, remarkably well 

 defined, with that of Sezanne. This relation becomes still more distinctly 

 shown by the few species of plants which have recently been added to it 

 and are described below. The flora is not vague or indefinite in its char- 

 acter; its types are clear. and precise; those which are limited to the 

 formation are found in the divers localities where the remains of plants 

 have been discovered, the relation of some others is with plants of a higher 

 stage, especially with those of the Miocene; very few are Cretaceous, and 

 these are mostly represented by persistent species which, derived from the 

 Jurassic, have passed through the intervening period to the present epoch. 



Though the geological surveys of the Government have not sent me 

 from the Laramie Group any specimens of fossil plants to be examined 

 and described in this volume, I have had the opportunity of looking over 

 a large collection of plant remains obtained at Golden for the Museum of 

 Comparative Zoology of Cambridge. They mostly represent species already 

 known. Of the new ones, none are referable to Cretaceous types; they are 

 still more generally allied to those of Sezanne. This does not imply thaf 



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