712 REVIEWS 
an account of their field occurrence and distribution, and a systematic 
description of their mineralogical composition and characteristics. The 
oldest rocks occur at the north end and consist of acid breccias found 
in remnants underlying early basic breccias. The former consist mainly 
of hornblende-andesite and hornblende-mica-andesite. The basic 
breccias consist of pyroxene-andesite, passing upward into basalt. Upon 
these were thrown other acid breccias, similar in composition and 
appearance to the earlier ones. These grade upwards into later basic 
breccia, consisting of andesites with less basalt than occurs with the earlier 
flows. ‘This last basic breccia forms the southern portion of the range 
within the park and also the Two Ocean Plateau. Remnants of surface 
flows of massive andesite form the summits of Mt. Stevenson, Mt. 
Doane, Colter Peak, and several prominent mountains south of Sylvan 
Pass. 
Chapters nine, ten, and eleven discuss different classes of the vol- 
canic rocks. ‘The Absarokite-Shoshonite-Banakite series consists of 
certain basaltic and other rocks associated with andesitic breccias 
and basalt flows which have considerable orthoclase and a compar- 
atively high percentage of potash. ‘They occur as lava flows and dikes 
in various localities. They have been classified according to their 
chemical and mineral composition. 
The rhyolites in the park are almost wholly extrusive lavas of 
uniform chemical composition, but differing widely in color, texture, 
and megascopic habit. ‘The mode of occurrence, and the microscopic 
features of phenocrysts, spherulites, lithophysae, are described in 
detail, and beautifully illustrated. The modifications of crystallization, 
lamination and the formation of pumice are referred to heterogeneity 
of the molten magma, especially with reference to the amount of vapors 
contained in it. In some places basalt appears to have been inclosed 
and partly fused by the rhyolite. 
The recent basalts are distinguished from the early brecciated ones 
by being ophitic and non-porphyritic. They overlie the rhyolite in 
most cases, but in some places they occur beneath it, and in some 
places between the older and younger sheets of rhyolite. 
With chapter twelve begins the paleontologic part of the work- 
The Director of the survey describes the Cambrian fauna from 
which twenty-one species have been obtained. Several of these are new, 
and are here described and illustrated for the first time. No fossils of 
undoubted Silurian age have been obtained. The Devonian is 
