X PKEFACE. 



W. Ashburner served as Assistant in the field from the com- 

 mencement of the Survey up to the spring of 1862, and was 

 chiefly employed, during that time, in examining gold-quartz 

 mines and machinery in the principal mining counties of the 

 Sierra Nevada. To all these gentlemen my cordial thanks 

 are tendered for their devotion to the interests of the Survey. 

 Rarely can it have happened, that one in charge of a work 

 of this kind has found himself more efficiently or more 

 pleasantly supported by his associates. 



We have also been greatly assisted by the use of collec- 

 tions and materials furnished by private individuals. I will 

 only specify in this connection such help as we have had in 

 what bears directly on the Palseontological Department, 

 leaving that which is related to the other branches of the 

 Survey to be fully set forth in other volumes. 



In the first place, the California Academy of Natural Sci- 

 ences has given us free access to its collections, among which 

 are some things of interest, collected chiefly by Dr. J. B. 

 Trask, which we should otherwise have failed of obtaining. 

 Dr. Trask has also frequently and most effectually aided 

 us by communicating valuable information as to localities, 

 as well as in other ways. Dr. J. A. Veatch has supplied 

 the Survey with extensive collections of fossils from various 

 localities, especially from the prolific one of Lick Springs, 

 or Tuscan Springs, as it is now called ; he has also contri- 

 buted valuable specimens from the Cerros Islands and from 

 Clear Lake. Mr. Gorham Blake has also made important 

 additions to our collections, by specimens contributed from 

 various quarters, especially from the Humboldt Mining 



