314 The American Geologist. May, isos 
schists, strongly suggesting their being about of the age of these 
schists. 
All of the evidence gathered by the United States Geological 
Survey goes to show that Mr. Mills' subdivisions of the pre- 
Tertiary rocks of the Sierra Nevada do not hold for the great 
mass of the central part of the range. 
It is also certain that the areas, as mapped by Mr. Mills (see 
plate 13) about the American valley, will need much modification. 
Thus a belt of argillite containing limestone* with Silurian fossils 
has been traced by Mr. Diller and the writer into the large Lower 
Mesozoic area of the Grizzly' mountain, and Mr. Diller has collected 
both Triassic and Carboniferous fossils in Mr. Mills' Lower Mesozoic 
area to the east of Red hill between the north fork and east branch 
of the north fork of the Feather river. 
The pre-Cretaceous age of the metamorphic rocks of the California Coast 
ranges; by Harold W. Fairbanks; American Geologist, March, 
1892. 
In this paper Mr. Fairbanks seeks to prove that the peculiar 
metamorphic rocks of the Coast ranges, silicified shales or phthan- 
ites, glaucophane schists and hardened sandstones are not altered 
forms of the lower Cretaceous (Neocomian) shales and sandstones 
as held b}'^ Whitne}' and Becker, but that they represent an older se- 
ries on which the Neocomian rocks (the Knoxville beds) and later 
Cretaceous are unconformably deposited. 
In a paper on the "Geology of mount Diablo, California,"! the 
writer assumed that the silicified shales and hardened sandstones of 
that mountain were of the same age as the Knoxville beds, although 
he found no convincing proof of this. He considered, however, 
that the diabase and serpentine at mount Diablo are of igneous 
origin, which conclusion Dr. Becker, after a visit to the district, 
concurred in. 
The diabase at mount Diablo seems clearly intrusive in the 
phthanites and hardened sandstones, and the metamorphic char- 
acter of these sedimentary rocks may be ascribed in part to the 
heat of the intrusive diabase. 
Supposing the diabase to be later than the Knoxville shales, it was 
thought remarkable, and noted in the paper above, that no dia- 
*This is the Montgomery limestone of Mr. Diller. See Bull. Geol. 
Soc. Am. vol. iii, p. 376. 
fBuU. Geol. Soc. Am., vol. 2., pp. 383-414. 
