32 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



to the south. Possibly these coastal eruptions can be 

 identified with some of the earlier Neocene volcanics 

 of the Sierra Nevada, and the Great Basin region. 



3. A slow and prolonged subsidence that effected 

 the development of a great accumulation of strata 

 known as the Monterey group, or "Monterey forma- 

 tion". In most parts of the Coast this group consists 

 largely of organic siliceous deposits of diatomaceous 

 shales, though containing other materials as well. It 

 is not coextensive with the Temblor group in area, 

 either within the Temblor Basin or outside of it. Its 

 fauna is scant and of boreal aspect, and it marks a 

 distinct change in the physical geography of the time. 



4. Uplift and folding and an interval of denuda- 

 tion and erosion, that must have been far reaching as 

 shown by its effects upon faunal development in the 

 epoch following. 



5. Subsidence that again extended the sea in the 

 Temblor Basin with the development of thick deposits 

 of largely terriginous sediments, not coextensive in 

 area with the preceding Monterey group, and resting 

 unconformably upon it. This subsidence was not so 

 profound as that of the Temblor or Monterey epochs 

 and led to the reintroduction into the basin of sub- 

 tropical species, as is shown in the faunas of the Santa 

 Margarita (San Pablo) deposits throughout the cen- 

 tral California coast. 



6. Uplift and local denudation, that again inter- 

 rupted the continuity of sedimentation in many parts 

 of the basin and probably in other regions, and that 

 was of sufficient extent in time or place to again effect 

 important faunal developments, as shown in the suc- 

 ceeding group. 



7. Subsidence that once more rearranged the dis- 

 tribution of land and sea about the Temblor basin, 

 with the development of a new group of sediments 

 known as the Etchegoin group, not coextensive in 

 area with the preceding Santa Margarita (San 

 Pablo) group, and not containing the same number 



