F. Dacite, east end of Chaos, northwest base of Lassen Peak. The youngest dacite of the region. Contains quartz, feldspar, biotite, and hornblende, embedded in a clear pumiceous glass. Analysis by W. F. Hillebrand, record No. 670. Described by Diller in Bull. 150, p. 218. G. Secretion in F. Consists chiefly of plagioclase and hornblende, with some olivine and clear glass. Analysis by Hillebrand, No. 671. H. Dacite (?), west side of old crater rim near the Thumb, at the head of Mill Creek, Shasta County. Shows phenocrysts of hornblende, plagioclase, and pyroxene, and apparently of quartz, in a gray, microlitic groundmass. Analysis by Hillebrand, No. 674.

I. Streaked dacite, falls of south fork of Bear Creek, Shasta County. Contains plagioclase with a little sanidine, hornblende, quartz, magnetite, some pyroxene inclusions, and glass base. Analysis by R. B. Riggs, record No. 524. P. R. C. 80. Described by Diller in Bull. 150, p. 213.

J. Dacite-tuff, Rice's quarry, 6 miles southeast of Paskenta, Tehama County. Clear glass, with fragments of quartz, feldspar, and hornblende. Analysis by George Steiger, record No. 1427.

K. Pyroxene-andesite, west end of Butte Mountain, Plumas County. Prominent phenocrysts of pyroxene and minute ones of plagioclase, in a dark groundmass containing much globulitic matter. Analysis by W. F. Hillebrand, record No. 411.

L. Pyroxene-andesite, south base of Burney Butte, Shasta County. Numerous small phenocrysts of plagioclase and a few of pyroxene, in a gray groundmass containing much amorphous matter. Analysis by R. B. Riggs, record No. 684.

M. Hornblende-andesite, Tuscan Buttes, 7 miles east of Red Bluff. A few small phenocrysts or fragments of hornblende, in a groundmass consisting mainly of plagioclase and gray microlitic matter. Analysis by Hillebrand, No. 412.

N. Hornblende-andesite, near Buntingville, Lassen County. A few phenocrysts of hornblende in a groundmass consisting mainly of small feldspars. Analysis by T. M. Chatard, record No. 413.

O. Hornblende-andesite, northwest summit, head of Burney Creek, Shast County. Inconspicuous plagioclase and, rarely, olivine, in a groundmass of plagioclase and pyroxene. Numerous dark spots are due to altered hornblende. Analysis by Riggs, No. 683. Rocks in this group dried at 105° before analysis.

P. Hypersthene-andesite, 1 mile west of summit on Bidwell's road, Butte County. Rich in small phenocrysts of plagioclase and pyroxene, mostly hypersthene, in a groundmass of the same minerals, with magnetite, and probably some amorphous matter. Analysis by W. F. Hillebrand, record No. 410.

Q. Hypersthene-andesite, old crater at head of Mill Creek. Contains small phenocrysts of plagioclase and hypersthene, in a groundmass of plagioclase, pyroxene, magnetite, etc. Some greenish pseudomorphs suggest former olivine. Analysis by T. M. Chatard, record No. 409.

R. Hypersthene-andesite, 2 miles south of Suppans Mountain, Tehama County. Abundant plagioclase and hypersthene, with traces of hornblende, in a microlitic groundmass. Analysis by Hillebrand, No. 672.

S. Secretion in R. Composed chiefly of plagioclase and hypersthene, with some quartz and amorphous matter. Analysis by Hillebrand, No. 673.

T. Hypersthene-andesite, westb ase of Suppans Mountain, near Lassen Peak, Tehama County. Contains numerous microscopic crystals of plagioclase and hypersthene, in a microlitic groundmass. Analysis by Hillebrand, No. 676.

Rocks dried at 100° to 110° before analysis.

U. Hypersthene-andesite, 1 mile southwest of Thumb, head of Bailey Creek, near Lassen Peak. Abundant but inconspicuous plagioclase and hypersthene, in a microlitic groundmass containing many small crystals of plagioclase. Analysis by W. F. Hillebrand, record No. 675. V. Hypersthene-andesite, west summit of Crater Peak, Shasta County. Microphenocrysts of feldspar and hypersthene in a groundmass consisting largely of the same minerals, with some amorphous matter. Analysis by Hillebrand, No. 679.

W. Hypersthene-andesite, north slope of Crater Peak. Phenocrysts of plagioclase and hypersthene in a groundmass containing much dark amorphous matter. Analysis by Hillebrand, No. 680.

X. Secretion in W. and a globulitic base.

Composed chiefly of plagioclase, hypersthene,
Analysis by Hillebrand, No. 681.

Y. Andesitic tuff, Stillwater Creek, 8 miles northeast of Redding. Contains plagioclase, hornblende, rare hypersthene, magnetite, and glass. Fragments of andesite are inclosed. Analysis by W. H. Melville, record No. 1346. Described by Diller in Bull. 150, p. 211. Rocks dried at 100° to 110° before analysis.

3D. BASALTS.

The quartz-basalts are described by Diller in Bull. 79. That from Mitylene was analyzed for comparison with the Cinder Cone series.

A. Quartz-basalt, Cinder Cone, 10 miles northeast of Lassen Peak. Contains plagioclase, pyroxene (mostly hypersthene), olivine, quartz, and much unindividualized base; the latter about 25 per cent. Magnetite is also present; augite occurs sparingly. Analysis by W. F. Hillebrand, record No. 407. P. R. C. 96. Also described in Bull. 150, p. 252.

B. Volcanic bomb from quartz-basalt, Cinder Cone. Analysis by Hillebrand, No. 665.

C. Lapilli from quartz-basalt, Cinder Cone. Analysis by Hillebrand, No. 667. P. R. C. 96. Also described in Bull. 150, p. 249. D. Volcanic sand, one-half mile northeast of Cinder Cone. Analysis by Hillebrand, No. 663.

E. White pumiceous inclosure from quartz-basalt, Cinder Cone. Analysis by Hillebrand, No. 664. Mainly glass.

Rocks dried at 100° to 110° before analysis.