Vor. IIT] ANDERSON—FURTHER STRATIGRAPHIC STUDY 3 
deed, at the time of the fire the present paper was in process 
of preparation and the manuscript was partly written; 
but on account of the destruction of the collections, its 
publication has not only been delayed, but in the form and 
matter of its contents it has been considerably altered and 
reduced. 
The general statements made in the earlier paper concern- 
ing the stratigraphic sequence in the Mount Diablo range, 
have proved to be fairly correct, and the same may be said 
of the formal statement of conclusions. It is only in their 
application within a certain definite portion of the field (and 
this within the area covered by the map) that any amendment 
is required. However, under a combination of circumstances, 
such error was unavoidable: In the first place, the field had 
been approached from the south, which was a direction of 
several disadvantages; in the second place, little was known 
from the literature concerning the general stratigraphy of 
the Eocene, and supposed Oligocene of the West-coast, 
and less concerning the geologic range of certain species 
of invertebrates, such as Pecten peckhami, and certain 
species of Tellina and Leda, and of several forms in the later 
‘Neocene. 
Since the former publication, however, some important ad- 
ditions have been made to the literature of the West-coast 
Tertiary, chiefly by Dr. Ralph Arnold* and by Geo. H. 
Eldridge and Arnold; and the paleontology of the Tertiary 
formations of the West has been somewhat enlarged. 
It is due also to remember certain observations made by 
Mr. J. S. Diller,” presumably upon the authority of Dr. Dall, 
regarding the occurrence of Pecten peckhami in the supposed 
Oligocene deposits of northwestern Oregon. While it may 
remain to be proved that the entire series described by Mr. 
Diller is properly referable to the Oligocene, it is clear that 
below a great thickness of sandy strata which are probably 
lower Miocene, there is a still greater series of ashy clay shales 
1Tert. and Quat. Pectens of Calif. U. S. Geol. Surv. Prof. paper 47, 1906. 
2See discussion of the oil districts of southern California in Bulls. 309 and 321, 
U. S. Geol. Sury. 
3U. S. Geol. Surv. 17th Ann. Rept. pt. 1, pp. 464-469. 
