774 JOHN C. MERRIAM 
extending below into the next group, and several species still 
farther down into the Chico group.” Since Gabb’s work was 
published the Tejon has been recognized at numerous points on 
the Pacific coast, outside the limits of its distribution as known 
to him, and has always been found to contain an easily recog- 
nized fauna, of which a number of the most common and char- 
acteristic forms are found in the list of species from locality No. 
5. As may be seen in the last quotation, the true relation of 
the Martinez to the Tejon, as shown by the partial mingling of 
species, was not unknown to Gabb. 
In the vicinity of the town of Martinez, the Martinez and 
Tejon groups form an apparently conformable series between two 
and three thousand feet in thickness and about equally divided 
between the two. The faunas, though overlapping, are in the 
main quite distinct and no great difficulty has been experienced 
by the writer in separating the groups on this basis. While some 
intermingling of species exists, it is not greater than we should 
expect to find in adjoining groups or periods. It should also be 
observed that the beds with a Tejon-like Martinez fauna and 
those containing an assemblage of characteristic Tejon forms are 
comparatively close together. The change from one fauna to the 
other may possibly have taken place in a short time by migra- 
tion, but we cannot assert positively as yet that the apparent con- 
formity of the beds is a real one, sedimentation may have been 
interrupted between the times of deposition of the two groups. 
It is at any rate quite clear that the two sets of strata, or two 
faunas, while belonging perhaps to the same series, represent dif- 
ferent periods in the geological history of California, periods 
quite as distinct, so far as faunal evidence is concerned, as the 
Miocene and Pliocene, or the Pliocene and Quaternary. The 
upper division of this series has already, on the grounds of its 
characteristic fauna, been named the Tejon. Toa mixed group 
of rocks, to which the fauna here called the Martinez gave indi- 
viduality, the name Martinez group was applied by Gabb. Itseems 
desirable, after having cut out the Chico portion of Gabb’s Marti- 
nez which was probably not the one on which he based the group, 
