merriam.] Fauna of the Lower Miocene in California. 



County seems to contain a somewhat larger number of recent 

 species than the T. hoffmani division and also lacks some of the 

 extinct species which belong to it. That this is probably not 

 simply a geographic variation in the fauna is shown by the 

 proximity of the T. Jioffmani beds of Ashley to the Agasoma 

 beds of Contra Costa County. 



When we come to study the subdivisions of the lower Miocene 

 both palaeontologically and stratigraphically some interesting 

 thing's relating to the movement of the Miocene shore lines are 

 suggested. The T. Jioffmani zone is found principally in the 

 western or coast region. The T. Ocoyana zone occurs in the 

 western region and also to the east of the great valley, where 

 the T. Jioffmani is not yet known. It would therefore, appear 

 that the sea had not reached as far east in the earliest Miocene 

 as it did later, and that the thick shale beds over the lower sands 

 of the western region were formed while sandy T. ocoyana beds 

 were being deposited to the east. 



University of California, 

 March, 1904. 



