XX PREFACE. 



Rocks of Tertiary age are extensively developed in the 

 Coast ranges, and especially in that portion of them which 

 lies between the parallels of 34° and 35°. Although fossili- 

 ferous in many localities, these beds do not usually retain 

 their organic remains in as good a state of preservation as 

 the Cretaceous, while the number of distinct groups of spe- 

 cies in the Tertiary rocks is considerable, indicating the 

 existence of several subdivisions of the system, the exact 

 relations of which to each other, and to those recognized in 

 the Eastern States and in Europe, are not yet fully wrought 

 out. Besides the marine mollusca of the Tertiary, to be 

 worked up by Mr. Gabb during the coming winter, there 

 are, in the collections of the Survey, large numbers of fossil 

 plants, as well as of mammalian remains, from the later 

 Tertiary and Post-tertiary of the Sierra Nevada and the 

 Coast ranges, which will be elaborated by competent author- 

 ities, and which will furnish, as is expected, the materials 

 for a second volume of the palaeontological portion of our 

 Report. 



For a full description of the Stratigraphical Geology of the 

 State, so far as developed, and for farther details as to the 

 distribution and relations of the fossils described in this vol- 

 ume, the reader is referred to the forthcoming volume of 

 General Geology, which is intended to follow the one here- 

 with presented without delay. 



J. D. WHITNEY. 



Office of the Geological Survey 

 of California, Sept. 1864. 



