842 UNITED STATES GEOLOGICAL SUEVEY— TERTIARY FLORA. 



in this flora only in the Lower Lignitic; none of its species are recognized 

 above, either by fruits or by leaves. In the description, the relation of four 

 species is remarked with the forms published by Saporta in the Suzanne and 

 the Gelinden Flora. The affinity of the species o^ Ndinnblum and Dombeyopsis 

 is with European forms of the lowest Miocene of Monte Promina, etc. The 

 Gretvwpsis species, also, all from the Lower Lignitic, have all their affinities to 

 ihe Eocene of Sezanne. The Aceracece and the SapindacecB are especially 

 representatives of the Miocene in Europe; the largest number is found at 

 ffiningen ; none of them have been recognized in the Eocene. In our Lig- 

 nitic flora, all the species except Sapindus caudatus belong to localities of the 

 third and the fourth group. Per contra, Rhamnus, which has in Europe a pre- 

 ponderance of its species in the Lower Tertiary of France, and the Lower 

 Lignitic of Germany and Switzerland, Haring, Monte Promina, Monod, is 

 limited by its American representatives to the Lower Lignitic, first and second 

 groups, for two of thera have been found at Evanston. Some of the Rham- 

 necR are considered in the descriptions of R. Goldianus and R. Cleburni as 

 probably identical to species described from Suzanne under a different generic 

 name. 



Of all the localities ascribed to the Lower Lignitic group, that of Point 

 of Rocks is particularly interesting, both by its flora and the position of the 

 strata, where, in 1875, Prof F. V. Hayden discovered rich deposits of vege- 

 table remains, and collected great numbers of finely preserved specimens, a col- 

 lection still increased by Mr. Cleburn's researches. This locality is between 

 Black Buttes Station, nine miles northwest of it, and Salt Wells, another station 

 of the Union Pacific Railroad, about the same distance farther west. From 

 Prof F. B. Meek's report, and from my own, it may be seen that from Black 

 Buttes to Point of Rocks, in following the railroad, the northwestern dip of 

 the measures brings successively in view a series of heavy sandstones inter- 

 stratified with beds of clay and lignite, whose whole thickness, as remarked 

 already (p. 25) is estimated, according to Messrs. Meek and Bannister, at about 

 four thousand feet. As Point of Rocks Station, where the specimens of Dr. 

 Hayden were found, is only a few miles from the cut end of the ridge, 

 east of Salt Wells, the thickness of the measures is there somewhat less, say 

 about three thousand feet. Though it may be, such a heavy series of strata 

 is passed from Black Buttes to Point of Rocks, that if any part of the so- 

 called Bitter Creek series is Cretaceous, we may expect to find, in the fossil 



