HUMAN REMAINS: DISCUSSION OF THE EVIDENCE. 283 
It appears probable on stratigraphical grounds, as will be set forth in a 
future chapter, that the detrital beds overlying the “bed-rock” of the 
Sierra Nevada represent the whole Tertiary period ; that is, that they have 
been forming since the beginning of that epoch. It also seems likely that 
there has been no break in the series of events; none, at least, of sufficient 
magnitude to justify the drawing of a sharp line anywhere, so as to say, 
above this is Pliocene, and below it is Miocene, or Eocene. 
The evidence as to the geological age of the gravel deposits afforded by 
the plants found in the sedimentary beds underlying the latest eruptive masses 
in the mining region of the Sierra has already been discussed by Mr. Les- 
quereux. He distinctly recognizes the presence in this flora of forms iden- 
tical with, or closely allied to, those of the Miocene ; but still calls the age of 
group Pliocene. Something of the same kind seems to be legitimately in- 
ferred from the animal remains of the same deposits. There are certain 
fossils which have been found only in deep-lying gravels, like those of Doug- 
lass Flat and Chili Gulch. No traces of the rhinoceros, the elotherium, or 
the small equine animal referred, with doubt, by Leidy to Merychippus, have 
ever been found in deposits which could by any possibility be proved to be 
more recent than the basaltic overflow. It is true that the evidence, thus far 
collected, is but fragmentary ; still, taking it for what it is worth, it may be 
said that the affinities of the animals found in these lower deposits would 
indicate a Miocene rather than a Pliocene age. There are also, it is believed, 
stratigraphical reasons for admitting that some, at least, of the deposits con- 
taining these older fossils may be proved, by other than paleontological 
evidence, to belong to an older series than those strata which, though an- 
terior to the basalts, yet contain a fauna decidedly more Pliocene than 
Miocene in character. This subject may, however, be discussed more at 
length, from the stratigraphical point of view, in a succeeding chapter. 
To draw the line between Pliocene and Recent, or to say whether between 
these two groups any distinct series of beds of an intermediate age exists in 
the fresh-water Tertiary of the Sierra, is a matter of even greater difficulty 
than to separate the Pliocene from a possible lower member of the series. 
It seems that the mastodon lived through a portion of the volcanic era, and 
flourished exceedingly down to a geologically recent period. The elephant, 
on the other hand, has not been detected in the beds below the basalt, so far 
as the writer can learn. That the fauna associated with these animals was 
entirely different from that now living in the same region is beyond doubt. 
