The crystalline rocks which occupy most of the 40,000 square miles of southern California range in age from Early pre-Cambrian to Quaternary. They include metasediments, plutonics, migmatites, complexes, volcanics, metavolcanics, and dikes.

Principal attention is given to the kinds, ages, origin, emplacement, distribution, and correlation of the widespread crystalline rocks. Thirty large areas, representing all important parts of southern California, have been chosen for special study and description. The writer has carried on field work in all these areas, has published papers on eight of them, and describes five of them here for the first time. Ten of the areas have been in part published upon by other workers, and in part reported on by the writer here for the first time. Seven of the areas have been more or less fully published upon by others. The work of others is critically reviewed, and various changes have been made in the light of field and laboratory work by the writer.

A chart, representing a more or less preliminary correlation of the principal crystalline rock units of the 30 areas, accompanies the paper. Correlational problems are discussed at length. The occurrence of fossils in various metasedimentary formations has greatly aided in the age determination of associated igneous rocks.

Another chart shows 29 chemical analyses of carefully selected igneous rocks, and their calculated modes and norms. Petrographic descriptions of these rocks are given.

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