432 University of California Publications in Geology [Vol. 8 



example, Astrodapsis whitneyi, a San Pablo species, and Chione whit- 

 neyi and (Chione) mathewsoni, Olig'ocene and possibly Lower Neocene 

 species, are reported to be associated with Echinarachnius excentricus, 

 a Recent Echinoid. 



Dr. C. E. Weaver, 32 at the time of the publication of his paper on 

 the Stratigraphy and Palaeontology of the San Pablo, appears to have 

 shared with Arnold the idea of the possible close relationship between 

 the San Pablo and the Purisima. After reviewing Arnold's and 

 Haehl's work on the Purisima, he concludes by saying that "at the 

 present time it is impossible to say whether the two formations are 

 equivalent or not." 



In 1909 Arnold and Robert Anderson 33 in a paper on the "Geology 

 and Oil Resources of the Santa Maria Oil District, Santa Barbara 

 County. California," gave a correlation table in which the San Pablo 

 is represented as occupying a lower stratigraphic position than the 

 Purisima. In this paper it is stated that certain beds in the Santa 

 Maria Oil District which had been included in the Fernando were to 

 be correlated with Fairbanks' Santa Margarita and Pismo formations. 

 No species characteristic of the Santa Margarita, however, were listed 

 by them. 



In 1909 Arnold's 34 paper on the "Palaeontology of the Coalinga 

 District" appeared. This was followed in 1910 by a final report on 

 the "Geology and Oil Resources of Coalinga District" by Arnold and 

 Robert Anderson. In these papers the marine Neocene, stratigraphic- 

 ally above what is known as the Vaqueros (Lower Miocene), is called 

 Santa Margarita and is correlated with the type section of the Santa 

 Margarita of Salinas Valley. A new formation, the Jacalitos, is de- 

 scribed and the Etchegoin formation, described by F. M. Anderson, 

 is recognized. 



Arnold recognized the distinctness of the fauna of the Santa Mar- 

 garita as compared with that of the Jacalitos and of the Etchegoin, 

 placing the former in the Middle Miocene and the latter two in the 

 Upper Miocene ; he considered the San Pablo of middle California to be 

 equivalent to the upper Jacalitos and lower Etchegoin, and younger 

 than the Santa Margarita. He states : 



For a number of years the Santa Margarita formation was believed to be the 

 equivalent of the San Pablo formation of the Mount Diablo region, but the 

 stratigraphic work in the Coalinga district has shown it to be older. It is 



32 Univ. Calif. Publ. Bull. Dept. Geo]., vol. 5, no. 16, pp. 243-269, 1909. 



ss IT. S. G. S. Bull. 322, 1909. 



34 U. S. G. S. Bull. 396, 1909; ibid., 398, 1910. 



