44 FOSSIL FLORA OF THE SIERRA NEVADA. 
degree which cannot be fixed on account of the deficiency of the speci- 
mens by which this last form is represented; Juglans Culifornica, com- 
parable to J. acuminata, var. latifolia, Heer, a species of wide distribution 
in the Tertiary, mostly Miocene, of Europe and of this country; and J. 
Oregoniana, which bears the same degree of affinity to J. mgella, Heer, of 
Alaska. Thus the Miocene or Tertiary facies of the flora of the Chalk 
Bluffs is manifested by four identical species, and by eight more or less 
intimately related to Tertiary species of this country or of Europe. It 
must be remarked, however, that, except the two species of Ficus, these 
last-named forms are truly intermediate in their relation, which, as seen 
here below, is quite as close with types of the present flora as it is 
with Tertiary ones. The comparison of these species, taken all together, 
gives a proportion of less than twenty-five per cent, as indicative of the 
Miocene character in the flora of the auriferous gravel. As the table 
shows, the more evident relation of the above species is with those 
recognized in the Tertiary of Alaska, and in the Lignitic of the Rocky 
Mountains by identity, more or less distinct, with Fagus Antipof, Populus 
Zaddachi, Ficus tiliefolia, F. microphylla, F. Greenlandica, this one only from 
Greenland; and that, therefore, the oldest types of the flora of the Chalk 
Bluffs are mostly American. Indeed, some of these types, as will be seen 
hereafter, may be clearly traced up to the Cretaceous of the Dakota 
group. 
The degree of relation of the plants of the above table with species 
of the present flora is much higher. As identical, as far as leaves may 
show identity, we find Betula cquals with JB. occidentalis; Fagus pseudo- 
ferruginea intermediate between F. ferruginea and F. sylvatica; Quercus 
Whitneyt with Q. lyrata ; Castanea chrysophylloides with C. chrysophylla ; Ulnus 
Califorimca with U. alata; U. pseudofulva with U. fulva ; Persea pseudo-Caroh- 
nensis with P. Carolinensis; Cornus ovalis with C. sessilis or C. Mas; Mag- 
nolia lanceolata and M. Calformeca with M. acuminata and M. cordata; Rhus 
typlinoides and R. metopiides with R. typhina and R. metopium. — Juglans 
Culifornica is referable to the old type J. acuminata, now represented 
only by the Asiatic J regia, widely distributed by cultivation. Besides, 
there is an evident, though less distinct relation between Quercus elcenoi- 
des and @Q. convexa with Q. virens and its variety; Q. Wevadensis with Q. 
castanea ; Q. Bowemana, Q. distincta, Q. Goepperti, and Q. Voyana with Q. agri- 
folia of California, and a group of Mexican Oaks, Q. crassifoha, Q. Hum- 
