AGE OF THE LIGNITIC DETEEMINED BY ITS FLORA 337 



In regard to the different localities ascribed to the Upper Green River 

 division, the flora gives positive indication of their synchronism. One of 

 the species most generally found, Planera longifolia, is common to all the 

 localities, Castello's Ranch, Florissant, Elko, and mouth of Wiiite River. It 

 has been found always in a profusion of specimens. Castello's Ranch and 

 Florissant have besides six species in common; Florissant and mouth of 

 White River, l^vo; Florissant and Elko, two; and Castello's Ranch and Elko, 

 one. The general and peculi.ar character of the flora is recognized at all the 

 localities; for exa\n\Ac, Salvinia, Myrica, and Sapindus are predominant in the 

 whole group, though there may be specific distinctions in the separate habitats. 

 The compounds also, a fine-grained shale, laminated in thin layers of about 

 half a centimeter in tliickness, buff-colored or reddish, wherein the remains of 

 plants are preserved, are the same in the four localities from which specimens 

 have been sent. All have, upon their smooth surface, a profusion of broken 

 or crushed remains of Conifers, leaves, fragments of stems, with scales of 

 fishes. This general character is not common to the Lower Green River 

 division. It has remains of fishes, but the matrix preserving specimens is a 

 yellowish sandy shale, coarser than that of the upper group, and more irregu- 

 larly flaggy. 



From the close relation of the flora of the fourth group with that of 

 Carbon, it seems that the climatic circumstances which have governed its 

 vegetation were about the same as those prevailing during the Middle or 

 Upper Miocene period. The preponderance of Conifers; of shrubs, Myrica, 

 Salix, Staphylea, Pal'mrus, Zizyi^hus, Rhus; of trees of small size, Planera, 

 Carpmus, etc., give to the flora a general aspect which recalls that of the vege- 

 tation of uplands or valleys of mountains. This facies is not contradicted by 

 the kind of trees recognized from the specimens; for, if Fagus, Castanea, Acer, 

 and Fraxinus are represented, there is nearly a total absence of Oaks. The 

 flora does not indicate, however, a lower degree of average temperature than 

 that of Carbon, and the difference in the vegetation seems rather to result 

 from its habitat at a higher altitude. The upheaval of the Rocky Mountains 

 evidently began at the end of the Eocene period. The strata of the Lower 

 Lignitic are tilted up in their whole thickness at the base of the mountains ; 

 those of the Upper Green River group, as seen in the Parks at Castello's 

 Ranch, etc., are horizontal, and in no way disturbed in their direction when 



their ends abut on the primitive rocks. The deposition of their materials, 

 22 T F 



