GEOLOGY. 
39 
the same appearance, as if formed of the same materials, but com¬ 
pacting and crushing seem to have gone a little further so as to obscure 
the organic remains. Almost all the shale of the upper division of 
the Monterey contains diatom remains where it has not undergone 
alteration into the hard varieties. The same is true of the soft 
shale wherever it occurs in the lower portion of the formation, the 
most notable example being at the very base of the Monterey on the 
San Julian ranch east of the junction of Salsipuedes and El Jaro 
creeks, where it is associated with hard flint and limestone immedi¬ 
ately overlying the fossiliferous limestone and conglomerate of the 
Vaqueros. There the shale is earthy, pure white, and full of diatoms. 
When the shale has undergone alteration and hardening into the 
porcelaneous and flinty varieties the constituent organic remains are 
usually obscured, but here and there even in these the impressions 
may be found preserved. Usually an examination under the micro¬ 
scope reveals scattering circular and oval areas, of slightly different 
composition or character from the surrounding rock, that look as if 
they might represent the forms of organisms. In speaking of the 
exposure of Monterey rocks between the mouth of Schumann Canyon 
and Lions Head on the southern flank of the Casmalia Hills, H. W. 
Fairbanks says : a “The basal portion of the series is composed chiefly 
of clear, flinty rocks, showing abundant remains of organisms visible 
to the unaided eye.” And in speaking of the harder varieties of 
Monterey shale in general of the Point Sal region he says: 6 “When 
examined with the hand lens much of the rock is seen to be thickly 
specked with little round dots, averaging, perhaps, a millimeter in 
diameter. Under the microscope * * * the circular areas did 
not appear as numerous as in the hand specimen, and were only 
faintly distinguished by clearer polarization.” 
Aside from the diatoms the rocks of the Monterey contain remains 
of minute Foraminifera, which have calcareous frames, and Radio- 
laria, which secrete silica to form their tests. The latter are present 
sparingly. The-common siliceous shale contains very little lime and 
no Foraminifera have been found in it in this district, although they 
have been reported from the typical Monterey shale elsewhere. 
R. M. Bagg c found 66 species belonging to 17 genera in chocolate- 
colored, soft, fine-grained shale of the same formation near Asuncion, 
San Luis Obispo County. J. C. Branner in the introduction to 
Bagg’s paper, describes the shale as follows: “The shale proper also 
varies; at some places it is flinty, at others it is somewhat sandy, 
and at still others it is soft and chocolate-colored, and contains an 
abundance of well-preserved Foraminifera. * * * The bulk of 
a Geology of Point Sal: Bull. Dept. Geology, Univ. California, vol. 2, No. 1, 1896, p. 9. 
b Op. cit., p. 10. 
c Miocene Foraminifera from the Monterey shale, California: Bull. U. S. Geol. Survey No. 268, 1905. 
