INTRODUCTORY NOTE. 



During 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 incurred 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. 0. 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- 



