The Tertiaries of California, although extensively developed, 

 and usually highly fossiliferous, are of such a character that the 

 included organic remains are rarely well preserved. No Eocene 

 has ever been detected in the State; the Miocene fossils are almost 

 invariably in bad condition ; and it is only from the later deposits 

 that good specimens have been obtained, unless in a few excep- 

 tional cases. 



As a consequence of this state of things, but few new species 

 have been found in these formations. Among about three hun- 

 dred recognized species, less than a fifth are new. The majority 

 of them are referable to living forms, while but a few can be 

 with certainty recognized as having been previously described in 

 the reports of Wilkes' Exploring Expedition, or in those of the 

 Pacific Railroad Explorations. The following are all that have 

 been collected since the preparation of the manuscript of the 

 Palaeontology of California, Vol. 2, Section 1, Part 1. Appended 

 is a list of the species recognized during the progress of the 

 Geological Survey, with the necessary synonymy. 



TA.L. VOL. II.— 7 ( 41 ) 



