Notice of Syenitic Rocks from California .— Turner. 379 
Levy. The above .classification manifestly does not provide 
for many rock-types of the syenite family, but is sufficient 
for the purposes of this paper. 
Although in the geological literature relating to California 
syenites and trachytes are often mentioned as occurring in 
that state, the writer knows of no authentic instance where 
rocks so called were determined by chemical or micro-optical 
methods. The trachytes have turned out to be hornblende- 
andesites and other rocks, and the syenites to be hornblendic 
granites and diorites. 
Aug it.e-syenite .— In a paper in 1895* mention was made of 
the occurrence of augite-syenite in Plumas county, near Ne¬ 
vada City in Nevada county where an area was discovered by 
Mr. W. Lindgren,! and as pebbles in Carboniferous conglom¬ 
erate in Amador county. The augite-syenite of Plumas 
county (Nos. 165 and 166 Sierra Nevada collection) forms a 
considerable mass about Hay Press valley in the southeast 
portion of the area of the Downieville sheet. It grades over 
into quartz-mica-diorite. These two granitoid rocks form, 
one large area, which appears to be of later age than the Jura- 
Trias rocks just west (called MiltonJ series provisionally) as 
there is evidence of contact metamorphism along the border 
of the Jura-Trias beds. 
Hornblende-syenite .— In 1893 Prof. C. D. Walcott brought 
back from Deep Spring valley in Inyo county a gray, rather 
coarse-grained granitoid rock, which was given to Mr. J. S. 
Diller for determination, and by him kindly referred to the 
writer as being most ‘interested in the region in question. 
This rock proved to be a hornblende-syenite. A partial 
analysis (No. 882, S. N.) is given in the table. It is composed 
of orthoclase, microcline, plagioclase, green hornblende, tita- 
nite, apatite and a little quartz. 
Soda-syenites .— In a report§ on the Sierra Nevada notice 
was given of the occurrence of white dikes in the serpentine 
near Meadow valley, Plumas county. Some of these dikes are 
composed of coarsely granular albite only (see No. 455 Plumas, 
in the table of analyses). Such a rock may be called an 
*Jour. Geol., vol. in, p. 390. 
fSee also text of Mr. Lindgren’s Nevada City folio, U. S. G. S. 
tSee American Geologist, vol. xm, 1894, p. 232. 
§Rocks of the Sierra Nevada 14th Ann. Rep. U. S. G. S., p. 477. 
