E. Phonolite, hill between Black and Big mountains, Uvalde quadrangle. Laurdalose. Contains sanidine, nephelite, and ægirite, and very little brown hornblende, augite, and magnetite. Sp. gr., 2.559, 19.5. P. R. C. 1070.

F. The portion of E soluble in 1:40 dilute nitric acid.

G. Nepheline-basalt, Tom Munns Hill, Uvalde quadrangle. UraldContains olivine, augite, nephelite, magnetite, and apatite. Sp. gr., 3.148, 19°. P. R. C. 1065.

ose.

H. The portion of G soluble in 1:40 dilute nitric acid.

I. Nepheline-basalt, Black Mountain, Uvalde quadrangle.

Urald

ose. Contains olivine, augite, nephelite. magnetite, and apatite. Sp. gr., 3.200, 21.5°. P. R. C. 1066.

J. The portion of I soluble in 1:40 dilute nitric acid.
K. Augite from I. Violet in color, very pure.

L. Nepheline-melilite-basalt, from about 3 miles southwest of Uvalde. Casselose. Contains nephelite, melilite, olivine, augite, magnetite, and apatite. Sp. gr., 3.150, 20.5°. P. R. C. 1064.

M. The portion of L soluble in 1:40 dilute nitric acid.

Rocks N to U collected by R. T. Hill in the trans-Pecos region. Descriptions supplied by Whitman Cross. Analyses, hitherto unpublished, by W. F. Hillebrand, record No. 1901.

N. Rhyolite, summit of Chisos Mountain, Big Bend of the Rio Grande. Liparose near alaskose. Pink porphyry. Rich in alkali feldspars and quartz, with very little riebeckite and barkevikite (?). Sp. gr., 2.602, 15.5°.

O. Rhyolite, near Shafter, Shafter quadrangle. Liparose near alaskose. Phenocrysts of sanidine and quartz. alkali-feldspars, quartz, riebeckite (?), and ægirite. traverse the rock. Sp. gr., 2.617, 15.5°.

Groundmass of Spherulitic bands

P. Rhyolite, north summit of Chisos Mountain. Liparose. Consists chiefly of alkali-feldspars and quartz, with riebeckite and a little magnetite. Sp. gr., 2.611, 15.5°.

Q. Rhyolite, west of Paisano Mountain, Alpine quadrangle. Liparose. Contains alkali-feldspars, quartz, arfvedsonite, and ægirite. Sp. gr., 2.635, 15.5°.

R. Grorudite, about 2 miles north of the summit of Chisos Mountain. Grorudose-pantellerose. Contains alkali feldspars, and subordinate quartz, with riebeckite and ægirite in irregular interstitial patches. Sp. gr., 2.648, 15.5°.

S. Pulaskite, Santiago Mountain. Nordmarkose. Consists of alkali feldspars, with subordinate ægirite, ægirite-augite, riebeckite, magnetite, and rare lovenite. Sp. gr., 2.581, 25.5°.

T. Syenite-porphyry, Iron Mountain, near Marathon. Nordmarkose. Contains many oligoclase-albite phenocrysts in a groundmass of alkali feldspar, with very little quartz. Titanite, apatite, and magnetite are present in small amounts. Sp. gr., 2.577, 15.5°.

U. Essexite, Big Hill Canyon, Rio Grande. Essexose. Contains predominant orthoclase, soda-rich plagioclase, and nephelite, with considerable augite, olivine, and magnetite, and small amounts of biotite and apatite. Sp. gr., 2.686, 25.5°.

LAKE SUPERIOR REGION.

1. MARQUETTE REGION, MICHIGAN.

Rocks mostly described by Van Hise and Bayley. When not otherwise specified the descriptions have been published in Mon. XXVIII, and partly in 15th Ann., p. 485.

A. Peridotite, near Opin Lake, E. sec. 27, T. 48 N., R. 27 W. Marquettose. Contains diallage, olivine, magnetite, and plagioclase. The diallage is partly chloritized, and the olivine is partly serpentinized. Analysis by W. F. Hillebrand, record No. 1452. P. R. C. 996.

B. Altered greenstone, Marquette district. Camptonose. Analysis by George Steiger, record No. 1586, hitherto unpublished. P. R. C. 988.

C. Grünerite-magnetite-schist, sec. 11, T. 47 N., R. 27 W. Mainly impure grünerite, with magnetite and quartz. Analysis by W. H. Melville, record No. 1403. P. R. C. 984.

D. Like C, from sec. 18, T. 47 N., R. 28 W. Analysis by Melville, record No. 1403. P. R. C. 980.

E. Like C and D, from sec. 20, T. 46 N., R. 30 W. Analysis by H. N. Stokes, record No. 1546. C, D, and E are similar schists, and alike in mineralogical composition. P. R. C. 981.