PENNSYLVANIA.

A. Aporhyolite, Monterey, Franklin County. Described by Florence Bascom in Bull. 150, p. 343. Contains alkali feldspars, quartz, sericite, epidote, titaniferous magnetite, leucoxene, and rarely sphene. Analysis by H. N. Stokes, record No. 1479. P. R. C. 136.

B. Quartz-porphyry, same locality. Analyzed for G. H. Williams, but never described. Analysis by L. G. Eakins, record No. 1350

DELAWARE.

Feldspars from gabbros. Separated by Diller, described by Chester in Bull. 59. Analyses by R. B. Riggs, record Nos. 459, 460, 461. A. Sp. gr. 2.592 to 2.877, from a typical gabbro, Brandywine Creek, Wilmington.

B. Sp. gr. 2.592 to 2.780, from a typical hypersthene-gabbro, Fifth and Van Buren streets, Wilmington.

C. Sp. gr. 2.592 to 2.749, from "Iron Hill hyperite changing to diorite," near Whitaker's ore pit.

Samples dried at 105°. FeO not determined separately.

MARYLAND, INCLUDING THE DISTRICT OF COLUMBIA.

1. PERIDOTITE AND PYROXENITE.

Rocks A to I, inclusive, described by G. H. Williams in Amer. Geologist, vol. 6, p. 35.

A. Porphyritic lherzolite, Johnny Cake Road, Baltimore County. Contains olivine, bronzite, and diallage, the olivine partly serpentinized. Analysis by T. M. Chatard, record No. 1094.

B. Pyroxenite, Johnny Cake Road. Consists entirely of hypersthene and diallage. P. R. C. 110.

C, D. Alterations of B. B, C, and D dried at 104°.

E. Smaragdite rock, altered pyroxenite, Dogwood Road, Baltimore County.

Analyses B, C, D, and E by J. E. Whitfield, record Nos. 975, 976. C, D, and E are from the laboratory record, and do not appear in the published paper.

F, G. Two samples of websterite, Hebbville, 6 miles west of Balti

more.

H. Bronzite from G.

I. Diopside from G.

The rock consists entirely of bronzite and diopside. Analyses by T. M. Chatard, record Nos. 1094, 1123.

J. Websterite, Oakwood, Cecil County. Composed of hypersthene and diallage. Analysis by W. F. Hillebrand, record No. 1755. Described by A. G. Leonard, but hitherto unpublished.

K. Cortlandtite, Ilchester, Howard County. Analysis by W. F. Hillebrand, record No. 1422. Published by Williams in Fifteenth Ann., page 674. The rock consists of olivine, pyroxene, and large hornblende crystals, the latter considerably altered to talc.

2. GABBRO AND DIORITE.

Rocks A to E, inclusive, described by G. H. Williams, but not in detail, in 15th Ann., pp. 673, 674. Some of the rocks, with other analyses, are discussed by him in Bull. 28. Analyses by W. F. Hillebrand, record No. 1422.

A. Olivine-gabbro, Orange Grove, Baltimore County. Contains plagioclase, diallage, hypersthene, fresh olivine, magnetite, and apatite, and sometimes hornblende.

B. Hypersthene-gabbro, Wetheredville, Baltimore County. Rich in hypersthene and diallage, with plagioclase, magnetite, and apatite. C. Gabbro-diorite, Ilchester, Howard County. A coarse anorthitehornblende rock, probably an altered gabbro.

D. Biotite-diorite, Triadelphia, Montgomery County.

E. Biotite-diorite, Georgetown, D. C.

To these may be added an apparently unpublished analysis made for Williams by L. G. Eakins, record No. 1350, as follows:

F. Hornblende-diorite, Rock Creek tunnel shaft, Washington, D. C. Relations to E not stated.