232 University of California Publications in Geology [Vol. 9 



relations could be established definitely, it would aid materially in 

 showing the close connection between the Merced Series and the 

 Purisima Formation south of Halfmoon Bay. 



The following species have been obtained from the Merced at 

 Pillar Point : 



Pelecypoda Spisula albaria Conrad 



Macoma, sp. Spisula hemphilli Dall 



Pecten oweni Arnold Gasteropoda 

 Phacoides annulatus Reeve Astyris riehthofeni Gabb 



Siliqua nuttalli Conrad Thais lamellosa Gmelin 



The presence cf Pecten oweni Arnold in this fauna points 

 toward a very close correlation between these beds and the Puri- 

 sima Formation a few miles farther south. It would also indicate 

 that they were slightly older than the beds at Seven Mile Beach, 

 since Pecten oweni has not been found in that section. However, 

 the absence of this form from closely related beds can hardly be 

 taken as proof of a later age. It is the opinion of the Avriter that 

 lateral distribution is an important factor in explaining the absence 

 of such forms from certain formations. The character of the sea 

 bottom, the geographic position of the basin of deposition, and 

 numerous other factors might have been unfavorable for the main- 

 tenance of such characteristic species. 



MERCED OF THE SARGENT OIL FIELD 



In Santa Clara County, west and southwest of Sargent Station, 

 there is an important occurrence of marine sediments, which con- 

 tains a fauna similar to the upper Purisima and Merced formations 

 along the coast. This formation has been called Merced and 

 Purisima by Mr. William F. Jones in his account of the geology 

 of this field. In the following discussion it will be referred to 

 as the Merced for the reason that there are beds beneath which 

 contain a number of species common to the lower Purisima which 

 are not common to the Merced. It seems advisable therefore to 

 use the name Merced in discussion of these beds. 



The Merced of this region covers a number of separate areas, on 

 both sides of the Pajaro River, and extending to the southeast for 

 several miles. In some of these areas the structure is monoclinal, 

 the strata dipping toward the east, while in others it is synclinal, 

 as in the case of the large area one mile west of Sargent Station. 



