AGE OF THE LIGNITIC DETERMINED BY ITS FLORA. 331 



is abundant at Florissiant, fourth group. Fhragmites should perhaps be, as a 

 genus, eUmiuated from the number of local representatives on account of the 

 uncertainty of the determination of the fragments; for, according to what has 

 been remarked in the description of the specimens referred to P. CEningensis, 

 they may be referable to divers generic types. Hence the distribution of 

 these fragments in most of the groups cannot be depended upon as evidence 

 of relation of age. The same might be said of Acorus branchystachys, found 

 at Black Buttes in jjoor specimens, their identification witii those of Carbon 

 and Florissant being doubtful. Then we have Flabellaria Zinheni in common 

 at Golden and Barrell's Springs. From the remark added to the descrip- 

 tion of the sjiecies, it is seen that the relation of the fragments from Barrell's 

 Springs is not ascertained, no more than the reference of the locality to the 

 third group. Then we have Populus mutahUis, which prevails in two localities 

 of the lower group,and is also found at Evanston ; Ficus itncata, described from 

 specimens of the Raton Mountains, Golden, and Carbon, or from the first and 

 third groups; Ficus tUicefolia, an omnipresent species, most common in the 

 European Miocene, and with us seen at nearly all the localities of the 

 Lower Lignitic, and also at Evanston in the Washakie group, and even 

 in the Pliocene of California. Cinnamonium affine also, which, common 

 in the Lower Lignitic, has been found at Carbon; Cissus parrotiafolla, a 

 rare species, seen at Marshall's, Mount Brosse, and the Lower Green River 

 group; Cissus lohato-crenata, found at Black Buttes and Mount Brosse; 

 Rhaiiinus rectinervis, common in the Miocene of Europe, as also in the 

 Lower American Lignitic, seen at Evanston; and then Jnglans Leconteana 

 and J. riigosa, two species which relate to or perhaps represent the most 

 common J. acuminata of the European Miocene, and which, rarely found at 

 Evanston, abound in different localities of the tirst groups. Quoting still a 

 small fruit, Carpites gluinaceus, obtained from Black Buttes and Evanston, 

 we have, as indicated in the table of these two hundred species of the Lower 

 Lignitic, sixteen only which pass into, or have been recognized in higher 

 groups of the Tertiary. This shows a unity and isolation of the Lower 

 Lignitic the more remarkable that none of its essential types, the Palms, 

 Magnolias, Grewiopsis, Viburnum, Rhamnus, etc., have, at least from what 

 is known now, passed above it. 



The second group, tliat of Evanston, has a peculiar flora, and thus an 

 indefinite relation, either in regard to the other divisions, or to the different 



