ROCKS OF THE COAST RANGES OF CALIFORNIA 495 
This list contains 5 forms belonging to the Miocene, 2 (57) 
forms belonging to the Merced formation, and 11 forms found 
elsewhere in the San Pablo formaticn. 
There are 17 extinct and 14 living species, and the formation 
may, therefore, be regarded as of lower Pliocene age, on the 
basis of the ratio of the living and fossil forms. 
In a recent paper,* on the Neocene sea-urchins, Dr. Mer- 
riam refers to the beds at Kirker Pass and similar beds at other 
points containing tuffs and volcanic ashes, as the ‘“‘San Pablo 
formation.” He considers the sea-urchins, belonging to the 
genus Astrodapsis, as particularly characteristic of this forma- 
tion, inasmuch as he has not found them outside of it, and his 
information concerning the formations covers other localities 
besides those mentioned in this paper. This series of strata will 
then hereafter be spoken of as the San Pablo formation. In the 
bulletin, above referred to, Dr. Merriam concludes that this 
formation is of Middle Neocene age, including the top of the 
Miocene, and the base of the Pliocene. In my bulletin on Mt. 
Diablo, I called attention to the similarity of the plant forms in 
the San Pablo formation of the region about Mt. Diablo with the 
plant remains of the Auriferous gravels formation of the Sierra 
Nevada. The collections of the plant forms from the Coast 
Ranges are not sufficient to narrowly correlate the plant remains 
from the two regions, but it is clear that the marine fossil shells 
of the San Pablo formation furnish a more certain criterion for 
determining the exact horizon of the formation, than do the 
plant remains. 
When the plant forms of the San Pablo formation have been 
collected in greater number and thoroughly studied a compari- 
son can then be made between the floras of the Auriferous 
gravel series, and of the San Pablo formation, and the age of 
the auriferous gravels decided on that basis. As pointed out 
in an article on the Auriferous gravels,? it is certain that the 
fossil leaves collected from different localities in the Sierra 
* Bull. Dept. Geol. Univ. of California, Vol. II, p. 116. 
? American Geologist, Vol. XV, June 1895. 
