7io 



INDEX 



Olenellus thompsoni, 412. 

 Oligocene, 573. 



climate of, 635. 



migration during, 639-640. 



of Atlantic and Gulf coasts, 577- 

 578. 



of other continents, 578. 



of Pacific coast, 578. 



of western interior, 578. 



physical geography of, 577-578. 

 Olivine, 691. 

 Oncoceras pandion, 434. 

 Oneida conglomerate, 441. 

 Oneida stage, 439. 

 Onondaga limestone, 452, 454. 

 Onychaster flexilis, 481. 

 Onychocrinus exsculptus, 481. 

 Oolitic limestone, 77-78, 249. 

 Ooze, 241. 



Ophileta compacta, 434. 

 Ordovician, 401, 418-438. 



climate of, 437. 



close of, 422. 



duration of, 437. 



in New York state, 422. 



life of, 427-437. 



of other continents, 423. 



oil and gas of, 424-426. 



physical geography of, 418-424. 



volcanic activity of, 423. 

 Ore deposits, 370-375. 



and magmatic waters, 371. 



in fissures, 370-371. 



origin of, 370. 



weathering and concentration of, 373. 

 Oreodon, 619. 



Organic deposits in lakes, 134. 

 Organisms and rock disintegration, 37. 

 Origin of the earth, 385-387. 

 Oriskany sandstones, 452, 454. 

 Orkney Islands, work of wind in, 44. 

 Orthaulax gabbi, 628. 

 Orthis tricenaria, 432. 

 Orthoceras, Devonian, 460. 



Mesozoic, 530. 



Ordovician, 435. 

 Orthoceras multicameratum, 434. 

 Orthoceratites, Carboniferous, 481. 



Mesozoic, 528. 

 Orthoclase feldspar, 689. 

 Orthoptera, 532. 



Osborn, H. F., 572, 578, 605, 611, 623 

 631,663. 



Ostracoderms, Devonian, 461-462. 



Silurian, 450. 

 Ostracods, 435, 436. 

 Ostrea sellaeformis, 628. 

 Ottoia prolifica, 415. 

 Oudenodon, 537. 

 Outcrops, width of, 253. 

 Outer Hebrides, 205. 

 Outliers, 106. 

 Outwash plains, 178. 

 Overdeepening, 163. 

 Overlap, 271. 

 Oversteepening, 163. 

 Overturned folds, 255. 

 Owens valley, earthquake of, 282. 

 Oxbow lakes, 121, 122. 

 Oxidation, 36. 

 Ozarkian, 401, 408. 



Pachyaena, 595. 

 Pahoehoe lava, 299, 300. 

 Palaeaster eucharis, 457. 

 Palaeaster simplex, 431. 

 Palaeomastodon, 613. 

 Palaeoneilo constricta, 459. 

 Paleodictyoptera, 483. 

 Paleogeography, definition of, 22. 

 Paleolithic man, 676-678. 

 Paleontology, definition of, 22. 

 Paleozoic era, 401-507. 



climate of, 507. 



life compared with Mesozoic, 521. 



change in life at close of, 521. 



evolution and extinction during, 506. 



physical geography of, 505-506. 

 Panama Canal, 34, 74, 280. 

 Paradoxides, 402, 412. 

 Paradoxides harlani, 412. 

 Parahippus, 610. 

 Pareiasaurus, 538. 

 Paris basin, 383. 

 Partiot, 218. 

 Pea ore, 442. 

 Peat, 134. 

 Pecopteris, 492. 

 Pecten madisonius, 628. 

 Pelagiella (Platyceras) primaevum, 413. 

 Pelecypods, Carboniferous, 481, 483. 



Devonian, 457, 459. 



Mesozoic, 526-527. 



Ordovician, 433. 



Silurian, 447-448. 



