Geol.— Vol. II.] ANDERSON— STRATIGRAPHIC STUDY l8l 



horizon on San Pablo Bay is equivalent to that of the lowest 

 horizon described in the Etchegoin Sands. Among the more 

 characteristic species are the following, from the bay-shore 

 north of Pinole : 



Astrodopsis turnidus Remond Mactra falcata Gould 



Pecten pablo'cnsis Conrad Pectunculiis seplentrionalis Midd. 



Pecten crassicardo Conrad Saxidomus aratiis Gould 



San Joaquin Clays. — The clays at the upper part of the 

 Etchegoin, from Coalinga northward, occupy at least a third 

 of the entire series, or about fifteen hundred feet in strati- 

 graphic thickness. At a distance these clays present a 

 banded appearance from the zones of color seen in the dif- 

 ferent strata, some of which have a width of two hundred or 

 three hundred feet. These clays are overlain by fresh water 

 deposits in the vicinity of Tulare Lake and the Kettleman 

 Hills to the depth of one thousand feet or more. 



No fossils have been found in them north of Coalinga, 

 but north of Tar Springs, Kings County, specimens of Scu~ 

 tella o-ibbsi and teeth of sharks have been found. 



^>' 



Tulare Formation. 



Overlying the San Joaquin Clays of the Etchegoin series 

 there are thick strata of gypsiferous sands and clays exposed 

 at intervals along the western border of the Great Valley. 

 In the Kettleman Hills, ten to fifteen miles southeast of Coa- 

 linga and near the western shore of Tulare Lake, these beds 

 aggregate fully one thousand feet in thickness, though no 

 attempt was made to measure them accurately. They lie 

 conformably upon the San Joaquin Clays and in some 

 respects resemble them, so that it is not always possible to 

 discriminate accurately betw^een them. Where the Tulare 

 beds are exposed in the Kettleman Hills they have been 

 noted by W. L. Watts S who gives a sectional view of the 

 Pliocene beds with which he classes these. Some of the 

 beds contain an abundance of fresh -water mollusks, and 



1 Bull. no. 3, Calif. State Min. Bur. 1894, p. 55. 



