122 UNITED STATES GEOLOGICAL SURVEY— TERTIARY FLORA. 



lobes, whicli, in all the specimens obtained, are flattened. A number of these 

 arc crushed and disfigured by compression, and the splitting at the top might 

 therefore be considered as casual or a 'i-esult of mere mechanical agency. 

 But I have carefully detached from the matrix some well-preserved nutlets, 

 like those of fig. 12, and all have the top flattened and split, though they 

 are cylindrical from above the middle to the base. I therefore consider this 

 character as original, and indeed, but for this, these fruits should be referable to 

 Oaks, their form being like that of species of acorns of the present flora; or to 

 nutlets of A^elu?nbiiim, the Sacred Bean, which they also resemble. I believe, 

 however, that they are referable to Palms. Their pericarp is of the same 

 color and consistence as that of Palmocarpon commune; it is in the same way 

 obscurely lined toward the truncate base as in P. truncatum, and the fruits are 

 found mixed with the specimens of these two species, and also in connection 

 with fragments of Palm or Sabal leaves. The truncate base is a character 

 of the fruits of some species of Sabal. 



Habitat. — Golden, Colorado ; Table Mountain. 



DICOTYLEDONES. 



Some of the fossii species of this division of the vegetable kingdom have 

 been found in Europe with leaves and fruits in connection with stems and 

 branches, even with flowers. In a few cases, therefore, an exact determina- 

 tion of these plants has become possible. But generally, and with scarcely 

 any exception in this country, the fossil species of dicotyledonous plants 

 are represented by their leaves only, and therefore their determination is 

 subject to a degree of uncertainty. The leaves, however, afford distinct, even 

 specific characters, by their form, their thickness, or consistence, especially 

 by their nervation. A number of botanists of celebrity — A. P. De Candolle, 

 Leopold de Buch, d'Ettingshausen, Heer, etc. — have attempted to determine 

 by rules the essential characters of the nervation of the dicotyledonous leaves, 

 and to represent them under peculiar names, in order to facilitate researches 

 and the study of palaeontology. Though the laws governing the distribution 

 of the veins in the leaves in comparison to their forms have not yet been fully 

 discovered, we have, in the description of our fossil leaves, to rely on and to 

 describe all the characters which render them identifiable, and therefore to 

 use all the materials obtainable for that purpose. The terminology serviceable 

 for the description of the forms of the leaves is generally known by botanists, 



