VIII CONTENTS. 



Chapter IX — Continued. Page. 



Shoshonite 339 



Banakite 347 



Similar rocks in Montana 351 



Chapter X. — The khyoutes, 'by J. P. Iddings 356 



Introduction 356 



Megascopical characters 357 



Vicinity of the Mammoth Hot Springs 357 



Obsidian Cliff 359 



Canyons of Gibbon River and Madison River 366 



Madison Plateau north of the Lower Geyser Basin 367 



Vicinity of the Lower Geyser Basin 369 



Upper Goy ser Basin „ 372 



Madison Plateau south of the Geyser basins 374 



Bechler Canyon 375 



Falls River Basin 377 



Pitchstone Plateau 379 



Red Mountains 381 



Vicinity of Yellowstone Lake i 382 



Natural Bridge 386 



North and east of Yellowstone Lake 387 



Vicinity of Yellowstone River 388 



Vicinity of the Grand Canyon of the Yellowstone 3S9 



Northeastern corner of Yellowstone Park 391 



Microscopical characters of the rhyolite 393 



Phenocry sts 394 



Quartz 395 



Sauidine 398 



Plngioclase 399 



Pyroxene 399 



Magnetite and titaniferous iron oxide 400 



Zircon 401 



Pseudobrookite 401 



Allanite and apatite .. 402 



Groundmass 402 



Glasses free or almost free from microlites 403 



Globulitic glass 406 



Microlitic glass 408 



Forms of growth of microscopic crystals 410 



Lithophysre 416 



Microgranular structure 422 



Relations of the various microstructures to one another in the rock mass 423 



Lamination and banding 424 



Variations in composition among the rhyolites 427 



Intermingled rhyolite and basalt 430 



Chapter XL — Recent basalts, by J. P. Iddings 433 



Ophitic basalt 436 



Basalts related to those with ophitic structure 437 



Very fine-grained basalts with minute phenocry ts 439 



Chapter XII. — Paleozoic fossils 440 



Section I. — Cambrian fossils, by C. D. Walcott 440 



Section II. — Devonian and Carboniferous fossils, by G. H. Girty 479 



