260 UNITED STATES GEOLOGICAL SURVEY— TERTIARY FLORA. 



secondary nerves are all equal in size, in direction, in distance, etc., and the 

 leaves pinnately nerved. The average divergence of the lateral veins ic 

 60°; they all curve more or less in traversing the areas, forming regular 

 simple festoons along the borders, and joined by nervilles about in right 

 angle and mostly simple. I have not been able to find any distinct traces 

 of areolation. I cannot compare these leaves to living species of Apciba; 

 but they have such a degree of similarity by their form and characters to 

 those o{ Apeibopsis Deloesi, Heer (Fl. Tert. Helv., iii, p. 41, pi cix. figs. 9-11), 

 that the generic relation seems evident. That these leaves, however, are 

 referable to Apeiha is not certain. I considered them at first as Ficus, then 

 as Rhamnus, and, indeed, their relation to Ficus, especially by the nervation 

 and the long petiole, which in fig. 5 is four and a half centimeters long, is 

 distinctly marked, but contradicted also by the size of the petiole, equal to 

 that of the midrib, or proportionate to it and not inflated. 



Habitat. — Black Buttes, Wyoming. Though the leaves are there 

 abundant enough in the sandy shale above the main coal, I have never 

 found any fruit comparable to those published under this generic name by 

 European authors 



ACERINEJ]. 

 ACERACEiE. 



ACER, Linn. 

 About thirty species of Maple are known in the flora of our time, all 

 inhabiting the temperate regions of the northern hemisphere, especially 

 Europe, North America, and Japan, where they are distributed in about the 

 same proportion. Europe has ten species; nine belong to the United States. 

 The European Tertiary formations have furnished to paleo-botanists a large 

 number of species, forty-six of which are described and recognized as refer- 

 able to the ditferent types of this genus, besides fifteen of uncertain attribu- 

 tion. From this we should expect to see it equally well represented in the 

 American Lignitic. It is, however, not the case, for the species described 

 here, and another from Alaska by Heer, are as yet the only ones from the 

 Miocene of this continent. The origin of the Aceracea appears to be recent. 

 Dr. Newberry has described as Acer pristinus a leaf from the Cretaceous of 

 the Dakota group. The specimen which I have seen a*^ the Smithsonian 

 Institution is very fragmentary, but evidently referable to the species which 

 I have considered, from more complete specimens, as a Liquidnmhar (Cret. 



