Ouachitite, dike near Maple Spring, 4 miles southwest of Hot Springs. Described by Kemp, in Ann. Rep. Geol. Survey Arkansas, 1890, vol. 2, p. 399. A dike rock of the monchiquite group. Contains abundant and conspicuous augite and biotite, magnetite, and minor accessory minerals in a groundmass considered by Kemp as glass. Calcite and other secondary products are also present. According to Pirsson, Journ. Geol., vol. 4, p. 679, the so-called "glass" in the monchiquites is really analcite. Analysis by L. G. Eakins, record No. 1023.

A. Quartz-pantellarite, Vieja Mountains, San Carlos, Presidio County. Description furnished by E. C. E. Lord. Contains anorthoclase, augite, and grains of quartz in a groundmass of ægirine augite, a brown hornblende, which is probably barkevikite, orthoclase, and quartz. Magnetite and apatite are present as accessory minerals. Analysis by George Steiger, record No. 1581.

The following rocks from Uvalde County were collected by T. Wayland Vaughan. Petrographic data furnished by Whitman Cross. Analyses by W. F. Hillebrand, record No. 1681.

B. Plagioclase-basalt, Pinto Mountain, Brackett quadrangle. Contains olivine, augite, plagioclase (labradorite), biotite, a very little alkali feldspar (?), magnetite, and apatite. Sp. gr. 3.118, 20°. P. R. C. 1067.

C. Basanite, Mount Inge, Uvalde quadrangle. Contains sanidine, nephelite, hornblende, augite, ægirine augite, olivine, magnetite, apatite, and a trace of pyrite. Sp. gr. 2.770, 20°. P. R. C. 1069.

D. Rock of basaltic habit, allied to C, 1 mile northeast of Big Mountain, Uvalde quadrangle. Contains alkali feldspar, augite, magnetite, and variable amounts of olivine, nephelite, ægirite, biotite, and zeolitic minerals. Sp. gr. 2.742, 23°. P. R. C. 1068.

E. Phonolite, hill between Black and Big mountains, Uvalde quadrangle. 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. Contains olivine, augite, nephelite, magnetite, and apatite. Sp. gr. 3.148, 19°. P. R. C. 1065.

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

I. Nepheline-basalt, Black Mountain, Uvalde quadrangle. Contains olivine, augite, nephelite, magnetite, and apatite. Sp. gr. 3.200, 21.5°. P. R. A. 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. 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.

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. 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. 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.