AGE OF TBE LIGNITIC liETEHMINED T,Y ITS FLOTIA. 335 



so-called coal of Elko Station is a slialy compound iiupregiiatcd by bit- 

 umen. The flora, whicii is already somewhat explored, hut which promises 

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

 has a character quite at variance with that of the other <rn.ups as seen 

 iier(; below. Taken altogether, it is represented by nin(;ty-tlirce species, of 

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

 The first impression in looking over the tal:)le of distril)ution must excite a 

 (lonl)t about the relation of age of these two sul)divisions in considering the 

 (Treat dissimilaritv of the characters of their representative idanls, for two 

 species only are found common to both, Ficus Innccolala and Salix media, 

 both European IMiocene. 'I'iiis dissimilarity may be accounted for l)y local 

 distribution, for the lower division is merely represented l)y one locality, the 

 cut-oflr near Green Kiver Station, from whieli Dr. Ilayden 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 

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

 regard to their age, Sequoia Heerii and Ilex dissindlis of Sago Creek, are 

 merely related to Miocene species, while Lygodiuin neuroptcroides of Barrell's 

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

 With this it has only Equisetum Haydcnli, which relates it to the second 

 group, and FJahellaria Zinkeni to the first. Hence we have, at the Green 

 River cut-off, a flora which has to be considered in itseli; 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 then- 

 compound, that I refer it to the 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 the Lower Green 

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

 represented by fragments of stems and leaves. The first is of geu(Mal 

 distribution; tiie second indicates an affinity with tlu^ North Miocene. It 

 has also Salix angusfa, wliich is Upper Miocene of Europe, and Jiiglans 

 Schimperi, without distinct afllnity. With the second group, it has in common 

 Populus arr.tica, Ficus pseudo-poptdus, and Juglans dcnliculata, also European 

 Miocene types; and with the tliird, Populus arctica and Cissus Parrot icefulia, 

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

 else as yet in our American Tertiary measures, w:e find, as identical to Euro- 



