TERTIARY AT SAN DIEGO, SAN FERNANDO, AND SAN PEDRO. 177 
t 
species are not identical with Oregon forms. ‘‘ Nucula decisa is similar to N. divaricata, and 
both, in their markings, resemble N. Cobboldii of the English Miocene. Mactra Diegoana 
is nearly related to the Oregon M. albaria." The little species Tellina congesta is one of the 
most abundant fossils at Monterey, where it covers slabs of rock many feet square. For figures, 
see Plate III. i 
BERNARDINO SIERRA AND SAN FERNANDO. 
The range of hills extending nearly east and west between the valley of the Santa Clara and 
the plains of San Fernando is composed of uplifted strata of argillaceous sandstone. The 
range extends nearly in the line of prolongation of the valley of Williamson’s Pass, and has 
an average elevation of 1,000 feet above the plain of San Fernando. There is thus a very con- 
siderable exposure of the strata, and they probably attain a great thickness. 
The pass of San Fernando is, unfortunately, not a deep break or ravine through the range, 
made by a stream; the strata are thus not favorably exposed to view. Their lithological 
characters were indicated to some extent by the debris and transported blocks found in the 
ravines, and from them it was evident that thick beds of a very compact and even-grained sand- 
stone occurred in the range. The strata in general, however, appeared to be soft and not 
indurated, being chiefly gravel, sand, and clay, principally the debris of granitic rocks. 
F'ossils.— The only fossils obtained from the formation were in a loose mass of the sandstone 
near the southern base of the Pass. The genera Ostrea, Pecten and Turritella are represented, 
but the specimens are so imperfect that they cannot be specifically identified. "They are, how- 
ever, sufficient to show the Tertiary age of the strata, and I am inclined to regard them as 
Miocene. The Eocene is very probably present at the base, and the Cretaceous may also occur. 
The range of hills separating the San Fernando plains from those of Los Angeles is formed of 
sandstone strata very similar to those of the San Fernando range, and I am inclined to regard 
them as of the same age. On the other side, or towards the north, the extensively developed 
strata exposed in the lower part of the Pass of San Francisquito, and in Williamson's Pass 
nearly to its summit, are so near the Tertiary formation of San Fernando, and appear to be so 
connected with it, that there is little doubt of their being a part of the same formation. We, 
however, do not find in the San Fernando range those thick strata of red argillaceous sandstone 
which appear in the passes. These may be referred to the lower part of the series, or may 
possibly be of the age of the upper Cretaceous. The interesting relations which these uplifted 
and folded sandstone strata bear to the adjoining granitic and metamorphic rocks, renders the 
determination of their age an important pee Their lithological characters and general extent 
are described in the Itinerary. 
LOS ANGELES AND SAN PEDRO. 
_ It is very probable that the strata of the ranges just described pass beneath the surface and 
form the gently sloping plains of Los Angeles and its vicinity. The surface is, however, so 
generally level and regular in its descent that it does not appear possible that the underlying 
strata are thrown into flexures or inclined at angles corresponding to those in the ranges. If 
the strata do extend seaward under the slope, they either become nearly horizontal, or the irregu- 
; 23 F 
