AGE OF TEE LIGNITIC DETERMINED BY ITS FLORA. 335 



so-called coal of Elko Station is a slialv compound impregnated hy bit- 

 umen. The flora, which is already somewhat explored, but which ])romises 

 for the future an abundant harvest of rich and very interesting materials, 

 has a character quite at variance with that of the other groups as seen 

 here below. Taken altogether, it is represented by ninety-three species, of 

 which thirty-four are credited to the lower division and fifty-nine to the upper. 

 The first impression in looking over the table of distribution must excite a 

 doubt about the relation of age of these two subdivisions in considering the 

 great dissimilarity of the characters of their representative plants, for two 

 sjjecies only are found common to both, Ficus lanceolala and Salix media, 

 both European Miocene. This dissimilarity may be accounted for by local 

 distribution, for Ihe lower division is merely represented by one locality, the 

 cut-off near Green River Station, from which Dr. Hayden obtained, when 

 the construction of the railroad was in progress, a number of fine speci- 

 mens. The two other localities ascribed to the section, Sage Creek and 

 BarreU's Springs, have too few species for points of comparison; and, in 

 regard to their age. Sequoia Heerii and Ilex dissimilis of Sage Creek, are 

 merely related to Miocene species, while Li/godium neuropleroides of BarreU's 

 Springs is of a peculiar type, without affinity to any other of the Tertiary. 

 With this it has only Equisehim Haydcnii, which relates it to the second 

 group, and FlabeUaria Zinkciii to the first. Hence we have, at the Green 

 River cut-off, a flora which has to be considered in itself, or which does not 

 offer any distinct affinity with that of the other Tertiary divisions. It is, 

 therefore^ on account of the geological distribution of the strata and of their 

 compound, that I refer it to tlie Green River formations. Some of its types 

 seem to indicate it as more recent than that of Carbon. 



With the first or Lower Lignitic group, the flora of tlie Lower Green 

 River has in common the two Fhrciginites, P. CEningcnsis and P. Alaskana, 

 represented by fragments of stems and leaves. The first is of general 

 distribution; the second indicates an affinity with the North Miocene. It 

 has also Salix angusta, which is Upper Miocene of Europe, and Jaglans 

 Schimpe.rl, witliout distinct affinity. With the second group, it has in common 

 Populus arrtka, Fictis pseudo-2}opiilus, and JugJarts denticulata, also European 

 Miocene types; and with the third, Populus arctica and Cissus Parrot ia folia, 

 already remarked upon. In the species which have not been found anywhere 

 else as yet in our American Tertiary measures, we find, as identical to Euro- 



