18 GEOLOGICAL SURVEY OF THE TEERITOEIES. 



The relation of all these species, therefore, except the Cyperacew, Sec, 

 found everywhere, is evidently with younger types, and indicates a 

 higher station in the Tertiary measures. From the absence of the 

 species which characterize the American formation considered as 

 Eocene, and also from the absence of the Arctic types, which become 

 less predomineut in advancing toward our present epoch, the fossil plants 

 of Green Eiver apparently represent the tipper Miocene. 



POINT OF rock: station. 



The horizon of this station, like that of the former, was left undeter- 

 mined in the Eeport, p. 308, the few specimens received from it indicat- 

 ing only one Cyperites, Fagus Antipofi, and indistinct leaves referable 

 to Juglans and Platanus. Nine species have been added to this short 

 list, from a new contribution of specimens ; but as none of them is char- 

 acteristic of a peculiar horizon, the geological station of this place is 

 not positively ascertainable. Of these species, Corylns McQuarrii, 

 Populus arctica, and Platanus Guillelmce are represented in the forma- 

 tion considered as Eocene, the first at 6 miles above Spring Caiion, the 

 two last at Evanston ; but they have been found also in connection with 

 strata referred to the lower Miocene — Medicine Bow, Washakie, and 

 Junction Station. Juglans rugosa is distributed through the whole 

 thickness of the American Tertiary, apparently at least ; the other spe- 

 cies, Gornus rhamnifolia, is found in all the stages of the European 

 Miocene. From the presence of a number of Arctic types, Populus 

 arctica, Platanus GuillelmcB, Yitis Islan'dica, Fagus Antipofi, which are 

 absent from the Green Eiver formation ; I believe, however, that Point 

 of Eocks occupies a lower stage in the Tertiary, though higher than 

 Evanston, and that therefore its place is in the Lower Miocene. This 

 supposition is essentially indicated by the absence of any of the species 

 marked as characteristic of the American Eocene. 



evanston. 



A lot of specimens representing especially species of Ficus is marked 

 in the former report, page 300, as of unknown origin. The lithological 

 characters of these specimens and the analogy of the species which they 

 bear, refer them to the same strata as those marked '■'■ Evanston, below 

 the coaV At the same place, the upper strata show evidently by their 

 remains of plants, representatives of a flora of the same age as the lower 

 ones ; for two of the four species recognized above the coal are found also 

 below it. Adding to this number the species described in these notes, we 

 have a list of 42 species of fossil plants for Evanston ; a larger number 

 than from any other locality of the American Tertiar3'. This place may 

 therefore be considered as a point of mark, used for future references 

 and comparisons. 



Considered in its whole or in its details, the large list of the species of 

 Evanston do not indicate any character which might modify the opin- 

 ion formerly advanced on the age of the formation. Except Morus affi,- 

 nis, closely allied to our living Morus rubra, all the other fossil plants 

 represent older Tertiary types. It is undeniable that without any ex- 

 ception most of these types of ours compared with European fossil spe- 

 cies should be referable to the Miocene. But as said in Eeport, pp. 313 

 and 314, either these species belong to the American Eocene or as yet 

 this formation is unknown in our geology. 



The relation of Evanston with the Mississippi Tertiary flora is 



