LESQUEKEux.] EVIDENCE OF AGE OF LIGNITIC GROUP. 291 



prints to it au odd physiognomy, it is either as remnants of the past, 

 merely recording a few features of old generations passed, away, or as 

 contemporaneous long persistent types, which do not distinctly charac- 

 terize any peculiar epoch. As proof of this assertion we have the true 

 Lower Eocene character marked in the same flora of Point of Eocks by 

 four species, Ficus planicostata, Vibitrnum marginatum, Populus me- 

 lanarioides, and Greviopsis Cleburni, which evidently, related to species 

 of the Sezane flora, though, in various degrees, have no affinity what- 

 ever to Cretaceous types. 



The flora of Point of Eocks is related to that of Black Butte by nine 

 identical forms or by one-third of its species. In considering the evi- 

 dence of synchronism, the identity of two floras could not be more posi- 

 tively proved than this, and nevertheless we have here two to thre^ thou- 

 sand feet of interposed measures. It is a remarkable fact, upon which 

 more will be remarked presently. The group of plants at Point of Eocks 

 has, besides the Eocene representatives, six species identified with, and 

 as many related to those of the Miocene of Europe. Therefore we see 

 here, what has been remarked in other localities of the Lignitic, a com- 

 pound or admixture of old and young tertiary types, in comparison at 

 least with the fossil floras of Europe, and thus a general character which 

 does not distinctly relate to any peculiar stage of European Tertiary. 

 "We have the Paleocene by relation to species of Sezane ; the Upper 

 Eocene, especially the Ligurian or Oligocene, by the Palms, and the 

 Miocene by a number of common and generally distributed forms which, 

 like Sequoia langsdorfii, Popitlus mutabiUSj Ficus tilicefolia, Ginnamomum 

 mississipiense. lihamnus rectinervis, Juglans rngosa, &c., are omnipresent 

 and constant types, indicating merely the Tertiary age for the Lignitic flora. 

 For this reason I shall continue to carefully record its points of aifinity with 

 the divers groups of the geological floras of Europe ; but at the same 

 time denying as yet sufficient evidence of identity to any of them I 

 persist to consider it simply as the Lower Eocene flora of this continent. 

 I said above that the identity of specific forms at Point of Eocks and 

 Black Butte was worth recording more carefully, as a remarkable 

 case in regard to the distribution of plants. In marine strata the long 

 preservation of types is a matter of little concern, for the circumstance 

 under which the marine faunas are distributed may be the same for very 

 long periods, as, for example, the mineral elements entering into the com- 

 pounds, the depth and temi^erament of the water, &c. But that a compara- 

 tively large number of land or fresh-water plants, subject to modifica- 

 tions or forced to migrations by atmospheric changes, may be preserved 

 identical through the lapse of time indicated by the thickness of the 

 measures heaped along Bitter Creek, has not been proved by as positive 

 an evidence as we have it here. The distance between both localities is 

 eleven miles only, and the superposition of the strata is all along so 

 clear, that there is no possibility of any mistake in the calculation of the 

 vertical space separating both i^oints. It is scarcely possible to hazard 

 a conjecture upon the length of time indicated by the building up of 

 these intermediate measures. Evidently of a shore formation, the heap- 

 ing of their materials may have been more rapid than for the deposits 

 at the wide bottom of the sea. They evidence, however, in their suc- 

 cession, a series of sandstone beds which though of greater thickness 

 are interstratified by beds of clay, built up of swampy deposits of long 

 duration and especially of coal-beds, still more clearly denoting the slow 

 progress of the work. 



A geological fact like the one remarked between the relation of the 

 floras of Point of Eocks and BlaQk Butte and the positive evidence of the 



