THE MARINE TERTIARY OF THE WEST COAST 611 
The most conclusive evidence of the Pliocene age of the Jacalitos 
and Etchegoin was the discovery of fossil land vertebrates in these 
formations in the Coalinga district. These vertebrate remains 
were obtained from three distinct horizons: one in what has been 
mapped as Jacalitos, another in the middle of the type section of 
the Etchegoin, and the third at the top of the Etchegoin. Pro- 
fessor J. C. Merriam, to whom this material was referred for study, 
has determined these faunas to be of Pliocene age. Merriam 
referred to the lowest fauna, that of the Neohipparion zone, as 
being not older than Lower Pliocene. The next horizon is fairly 
well up in the Pliocene, and the fauna from the upper Etchegoin is 
_ referred to the Upper Pliocene. 
It is interesting to note that stratigraphically above the Plio- 
hippus proversus beds of Merriam (uppermost Pliocene), in the 
above-mentioned section, there are several thousand: feet of land- 
laid deposits which are folded and are older than the Pleistocene 
terraces of that region. No evidence of the exact age of these 
beds has been obtained, but it is suggested that they may be the 
land-laid equivalent of the Saugus of that vicinity. 
Climate.—One of the most interesting results of the study of 
the invertebrate faunas of the Pliocene is the evidence they give 
of temperature differentiation. The fauna from the Wildcat and 
Merced of northern and middle California is essentially boreal in 
character. In southern California the Pliocene is for the most 
part represented by a fairly warm-temperate fauna. These two 
faunas, the boreal and the warm-temperate, have very little in 
common, and consequently it was a long time before their con- 
temporaneity was recognized. ‘The solution of the problem was 
obtained from the fauna of an intermediate area. The fauna of 
the type section of the Purissima in the Santa Cruz Mountains of 
California is in part warm-temperate and in part boreal, and cer- 
tain species very common in the north, some of which are fairly 
highly ornamented forms, were found in this section. 
Paleogeography.—It was noted in the first paragraph, under the 
discussion of the factors causing the differentiation of faunas of 
1J. C. Merriam, ‘‘Tertiary Vertebrate Faunas of the North Coalinga Region of 
California,” Amer. Phil. Soc. Trans., N.S. Vol. XII, Pl. III (1915), pp. 26-43. 
