INDEX 



7" 



Pelecypods — (Continued) 



Tertiary, 626, 627, 629. 

 Pelee, Mount, 306. 

 Pelycosaurs, 490. 

 Penaeus meyeri, 532. 

 Penck, A., 658. 

 Peneplain, 114, 1 15, 116. 

 Peneplanation, in, 114-118. 

 Pennsylvanian period, 401, 472-475. 



coal of, 473. 



duration of, 475. 



in other continents, 475. 



iron and oil of, 475. 



oil of, 475. 



physical geography of, 472-473. 



thickness of, 473. 

 Pentacrinus, 525. 

 Pentacrinus fossilis, 525. 

 Pentamerus oblongus, 446. 

 Pentremites pyriformis, 481. 



robustus, 481. 

 Peorian stage, 649. 

 Perce Rock, Quebec, 210, 21 1. 

 Peridot, 691. 

 Peridotite, 330. 

 Perisphinctes achilles, 529. 

 Perissidactyls, 599-600. 

 Permian, 401, 476-480. 



aridity of, 505. 



decrease in marine life, 504. 



deserts, 477. 



glaciation, 476-477, 505. 



gypsum, 476. 



in other continents, 479. 



physical geography of, 476-480. 



problems of, 504-505. 



volcanic activity of, 477. 

 Petrifaction, 378. 

 " Petrified moss," 66. 

 Petroleum, see Oil. 

 Petrology, definition of, 21. 

 Phacops rana, 460. 

 Phenacodus, 598, 600. 

 Phillipsia major, 484. 

 Phororhachus, 623. 

 Phosphates, Miocene, 580. 

 Phragmoceras parvum, 448. 

 Phyllograptus angustifolius, 428. 



typus, 428. 

 Physical geography, ancient, determina- 

 tion of, 403. 

 Physiographic geology, definition of, 21. 

 Piedmont glaciers, 167-168. 



Piedmont plains, 127. 

 Piedmont Plateau, 91, 92. 

 Pine, Arizona, natural bridge of, 65. 

 Pipestem concretions, 77. 

 Piracy, stream, 102, 107-109. 

 Pirsson, L. V., 332. 

 Pitch, 256. 

 Pitchstone, 332. 

 Pithecanthropus, 623. 

 Pithecanthropus erectus, 675. 

 Placer gold deposits, 374. 

 Placodermata, 464. 

 Plagiaulacidae, 591. 

 Planes of stratification, 24. 

 Planetesimal hypothesis, 386-387. 



contrasted with nebular, 387. 

 Planetesimals, 386. 

 Plants and chemical disintegration, 37. 



mechanical action of, 33. 

 Plants, Cambrian, 409-410. 

 Carboniferous, 491-498. 

 Devonian, 467. 

 Mesozoic, 565-568. 

 Ordovician, 436. 

 Pleistocene, 667-668. 

 Tertiary, 630-634. 

 Plastostoma broadheadi, 482. 

 Plateaus, see Mountains. 

 Platte River, a braided stream, 87. 

 Platyceras dumosum, 459. 

 Platycrinus discoideus, 481. 

 Platyostoma (Diaphorostoma) niagarense, 



447- 

 Platystrophia lynx, 432. 

 Playas, 134. 



Plectambonites sericeus, 432. 

 Pleistocene period, 573, 643-674. 



changes of elevation at beginning of, 



643-644. 

 duration of, 658-660. 

 glaciation of, 644. 

 life of, 663-683. 

 plants of, 667-668. 



sources of knowledge of life of, 663- 

 666. 

 Plesiosaurs, 554-555. 

 Pleurocystis filitextus, 430. 

 Pleurodictyum stylopora, 456. 

 Pleurophorus tropidophorus, 483. 

 Pleurotomaria nodulostriata, 482. 

 Pliocene epoch, 573. 

 climate of, 635-636. 

 elevation during, 587. 



