370 The American Geologist. June, 1902. 
roughly stratified, subangular gravel and clay which seem to 
form low Quaternary ridges on the south. 
CONCLUSION 
I will conclude this paper by evidence tending to fix the 
age oi the Rosamond and Escondido series. While studying 
the latter in the field I thought I was dealing with a Middle 
Pliocene series equivalent to the Berkeleyan and to the andes- 
yte-basalt epoch of the Sierra Nevada region, and the Rosa- 
mond series I correlated with the Lower Pliocene rhyolytes 
and rhyolyte tuffs about the bay of San Francisco and in the 
Sierra Nevada region; but evidence is accumulating that both 
are Eocene in age, which illustrates how dependent students 
of stratigraphic geology are on the paleontologists to straight- 
en out schemes of classification. 
Cajon pass, in San Bernardino county, is due to a north- 
west-southeast fault, obliquely traversing the Sierra Madre- 
San Bernardino range. Along the fault line there is a nar- 
row strip of Tertiary formations thrust down deep into the 
granite and schist complex. There are remnants of a dull 
vellowish or light brown, well stratified, fine sandstone, with 
some shaly and white layers suggestive of the Miocene bitum- 
inous shales. There are traces of marine fossils. At one place 
a coarse basal breccia-conglomerate was developed where the 
brown sandstone rested on the granite. The general appear- 
ance indicates the Monterey formation. 
Of much greater extent is a pink conglomerate and 
sandstone, which extends in a nearly continuous but narrow 
belt virtually entirely through the pass. It is especially de- 
veloped west of Cajon station. It is usually tilted at angles 
of 20 to 60°, averaging about 30°. The direction varies be- 
cause it is tightly pinched in between steep granite and schist 
ridges, but it is prevailingly northeasterly. The thickness may 
be several thousand feet but no .data for a careful estimate 
were taken. The conglomerate is chiefly of granite and schist 
and is coarse, boulders not being uncommon. It is well lithi- 
fied and commonly outcrops in great ledges making the struc- 
ture very plain. Its general appearance is like certain phases 
of the basal conglomerate of the Escondido series and for a 
variety of reasons I think they are identical. 
