204 University of California Publications in Geology [Vol. 7 



to designate the lower Miocene sandstone in the area under dis- 

 cussion " (p. 19). A fossil list, the most complete published up 

 to that time, is given with those fossils supposed to be charac- 

 teristic of this horizon indicated by asterisks. 



Returning to the overlying shales, they say "These shales 

 represent at least a part of the Monterey series, 43 which is sup- 

 posed to be of middle Miocene age" (p. 20). A list of fossils 

 is given for the Monterey and those characteristic of the horizon 

 designated. It is said, however, ' ' The upper part of the Vaquero 

 sandstone series, at least that part showing alternating beds of 

 sandstone and shale with a tendency to grade from sandstone 

 vertically upward into shale, may be the inshore equivalent of 

 some of the Monterey shale found at the typical locality in the 

 region around Monterey." The faunal character of this over- 

 lapping portion is not explained. 



The F ormation-F aunal Stage Fallacy. — Irrespective of whether 

 we agree or do not agree with Haehl and Arnold's determination 

 of the particular beds in San Mateo County as "lower Miocene" 

 and "middle Miocene" respectively, this idea of the "Vaquero 

 sandstone" and the "Monterey shale" as representing two dif- 

 ferent time intervals determinable by fossils paved the way for 

 much confusion which actually followed. The fundamental 

 trouble lay in this idea : These formations, where studied, could 

 be divided lithologically into two groups called by two forma- 

 tional names ; palaeontolo<iieal studies showed that there were 

 two distinguishable faunas supposed to represent two different 

 time intervals ; therefore these two faunas correspond to the 

 two "formations." which latter must then have been deposited 

 in these two different periods of time. The far-reaching effects 

 of this fallacy will be shown in following the later history. 44 



*3 Thus using Monterey series not in accordance with its previously 

 established usage, but corresponding to the "Monterey shale" of Hamlin 

 and Fairbanks. 



44 As far back as 189."), G. H. Ashley had published in the Proc. Cal. 

 Ac-ad. Sci., 2d Series, vol. 5. pp. 273-367, and in brief form in Jour, of 

 Geol., vol. 3, pp. 434-454 (1895), a discussion of the "Neocene Stratig- 

 raphy of the Santa Cruz Mountains of California," in which he attempted 

 to establish two series — the Pescadero and the Monterey-Merced. He 

 considered each of these to be a practically conformable series with per- 

 haps slight local breaks in them. In the former he included stratigraph- 

 ically the San Francisco sandstone of Telegraph Hill and other parts of 

 San Francisco, and of San Bruno Mountain (generally accepted as 



