564 H,. W. FAIRBANKS 
hitherto unrecognized paleontologic group. These strata it 
appears overlie those of the Contra Costa county Miocene with 
indications of a nonconformity, but the fossils collected from 
them by earlier palaontologists have in some cases been referred 
to the Miocene, in others to the Pliocene. To this series of 
rocks Dr. Merriam has given the name San Pablo formation. 
As the group of rocks in the southern Coast Ranges is undoubt- 
edly the equivalent of those on San Pablo Bay, the latter name 
will be extended to it. In the San Luis Obispo region the non- 
conformity of this series of rocks with the Monterey series iS 
distinctly shown in many places. Good examples appear along 
the coast north of Pismo as well as in the vicinity of Santa 
Margarita in the upper Salinas Valley. The basal conglomerates 
of the San Pablo formation, often but little disturbed, lap over 
on the more highly tilted and disturbed shales and contain many 
fragments of the latter often filled’ with mollusk borings. A 
great interval of time must have separated the deposition of the 
San Pablo formation from that of the bituminous shales, for the 
former formation extends over the shales in places and rests 
directly on the Golden Gate series. This time must have been 
sufficient for the erosion of at least 5000 feet of the Monterey 
series. During this time also the chief chemical change was 
wrought in the bituminous shales, for pebbles of the flinty 
altered shales occur at the base of the San Pablo formation in 
exactly the same condition as the shales on which this formation 
rests. 
The discovery by Dr. Merriam of the marked paleontologic 
differentiation of the fauna of this group of rocks is an impor- 
tant addition to our knowledge of the younger formations of 
the Coast Ranges. That it is not a local condition is shown 
by the results reached by the writer along different lines and 
wholly independently. The pronounced nonconformity so 
clearly apparent in the San Luis Obispo region is confirmatory 
of the paleontologic investigations and firmly establishes the 
validity of the new formation. Its fauna is certainly older than 
that of the Merced beds, and if it should prove to be the upper- 
