378 The American Geologist. Jane, 1895 
are all open to question. With more or less uncertainty the f(>llowin<( 
species have been determined: 
Fleets sordida Lx. ? 
Fie us shastensis Lx. ? 
Populns zaddachi Heer? 
Platanus appendicidata Lx.? 
Quercm sp. ? 
Fersea diUeri Lx.? 
Plant steins. 
Of theso. Fieus sordida, Popvlus saddacJti and Plafanus appendimlata 
come from the Auriferous gravels at Chalk blutl's, Nevada count}', and 
Ficvs shastensis and Pei'sea dilleri from the Miocene so-called, of Shasta 
county. While it is manifestly unsafe to draw very definite conclusions 
from these meager data, it is probable that the age is Miocene." 
The Volcano Hill beds probably belong to the lone forma- 
tion and are so represented on Lindgren's Sacramento geologic 
atlas sheet. The hill is not indicated by name on the map. 
It is on the ridge north of Rock creek, about three and a half 
miles north of Folsom, and about one-half mile west of the 
road to Rocklin. The hill is composed mostly of coarse gran- 
itic sandstone with some fine grained layers, in one of which 
the fossil leaves were collected. The sandstone of the top is 
irregularly eroded and reddened in places, looking somewhat 
as if burned, and the hill probably took its name from this 
peculiarity. The strata are approximately horizontal. The 
surrounding rock is granite. 
The age of the Auriferous gravels has been discussed and 
the literature. bearing on the subject reviewed by Diller in his 
paper on "Revolution in the topography of the Pacific Coast,"* 
which is an abstract of a fuller article to appear in the four- 
teenth annual report of the director of the U. S. Geo- 
logical Survey. Prof. Diller concludes from the evidence he 
presents that the Auriferous gravels are largely of Miocene age? 
and uses this evidence to prove the same age for the old sur- 
face of erosion of the Sierra Nevada, which has been preserved 
intact at many points under the "volcanic cement" flows. That 
this old surface of erosion was formed during the Auriferous 
gravel period seems unquestionable. Prof. Diller also con- 
siders that an old peneplain at the north end of the Sacra- 
mento valley is continuous with and of the same age as that 
of the Sierra Nevada, while Lawson suggests in his paper on 
*Journal of Geology, vol. ii, pp. .32-54. 
