496 H. W. TURNER 
Nevada from the Auriferous gravels formation represent differ- 
ent horizons; nevertheless, no distinction has been made thus 
far by the paleeobotanists, who have examined the different col- 
lections. It is, therefore, probable that, when studied, certain 
of these localities will be found to furnish a flora similar to that 
of the San Pablo formation, and other localities will furnish 
floras of a somewhat older date. In general, in recent years, 
the fossil plant remains of the auriferous gravels have been 
called Upper Miocene. It is more than likely that some of these 
localities are of Pliocene age. There is published herewith, a 
section of the San Pablo, formation at Kirker Pass, north of 
LEAVES 
Fic. 1.—Section of the San Pablo formation on the Hyde Ranch, north of Mt. 
Diablo. The horizontal extent of the section is about 600 meters. ‘The section, how- 
ever, does not necessarily include the top or the base of the formation at this point. 
A —White shales and rhyolitic tuff; = Fossiliferous sandstone; C= Andesitic 
tuff, sandstone, and conglomerate; = Shale and pumice. 
Mount Diablo. The horizontal extent of the beds shown in the 
section is 600 meters. The beds dip uniformly to the north at 
an angle of about 35° and thus have a thickness normal to the 
bedding of about 350 meters, or about 1150 feet. The section 
given above (Fig. 1) is drawn without reference to scale, merely 
to show the relations of the different members of the formation. 
The basal portion (4) of the section is composed of fine-grained 
white shales, and volcanic detritus, which Dr. Merriam has noted 
at other localities in the formation, and he regards this as its base. 
An optical examination of volcanic glass which forms certain 
layers in these white shales, shows the glass to be of rhyolitic 
composition. There is given below an analysis, No. 399, of a 
specimen of this glass. This analysis shows that the rhyolite 
has undergone leaching, having lost both alkali and silica, as is 
