INTRODUCTORY NOTE. 
Durine the first three years of the existence of the Geological Survey 
of California, large collections of specimens were made in various parts 
of the State, and especially in the mining districts of the Sierra Nevada. 
Unfortunately these were in part destroyed by fire, and among the mate- 
rial thus lost was a fine suite of fossil leaves from the beds underlying 
the volcanic deposits of the west slope of the Sierra, and associated with 
the auriferous gravels so extensively worked by the hydraulic process. 
The loss thus mcurred was in part made good by a collection of fossil 
plants placed at my disposal by Mr. C. D. Voy of Oakland, the speci- 
mens thus furnished forming a portion of the large collection purchased 
afterwards from Mr. Voy, and presented to the State University of Cali- 
fornia by the liberality of Mr. D. O. Mills of San Francisco. The speci- 
mens in question were subsequently placed in the hands of Mr. Lesque- 
reux for description, and to these were added some other materials of 
value, chiefly obtained by Mr. Gorham Blake and myself, at the prolific 
locality of Chalk Bluffs. 
A full account of the formation in which these fossil plants occur 
will be found in the writer’s “Memoir on the Auriferous Gravel Deposits 
of the Sierra Nevada,’ which will shortly be published as Part I. of 
the volume to which the paper herewith presented belongs. It has 
been thought best, however, not to delay the issue of the paper of Mr. 
Lesquereux, as it forms a nearly independent contribution to the geological 
history of the Sierra Nevada, and marks an important addition to our 
knowledge of the epoch immediately preceding the present one, giving 
as it does a clew to the vegetation, in later Tertiary times, of an exten- 
