2O4 



INDEX 



Ordovician period, 46, 79, 111, 113, 



119, 144 

 Organic deposits, 58 



habitats, areal variability in, 78 

 Organism, 105 

 Organisms, bionomic relations of, 108 



individuality of, 87 



origin of, 106 

 Orion, 8 



Osborn, H. F., 104 

 Ostracoderms, 119 



origin of, 111 



Over-specialization, indications of, 131 

 Owens Lake, 185 

 Ox, 177, 178 

 Oxalates, 107 

 Oxides, 100 

 Oxygen, 44, 51, 102 



importance of, for life, 92 



in primordial atmosphere, 34 

 Ozark uplift, 62 



Paleogene time, 79 



Paleogeography, 66, 72, 77 



Paleozoic era, 46, 64, 65, 76, 78, 79, 



111, 127 



era, North America in, 62 

 era, time ratio of, 69 

 sediments, thickness of, 65, 67 



Palms, 184 



Panama land-bridge, 74 



Pasteur, L., 93, 182 



Patten, W., 119 



Peabody Museum of Yale University, 

 123, 133 



Penck, A., 187 



Peneplanation, 76 



Pennsylvanian period, 46, 66, 76, 79, 



111, 127 



period, diastrophism in, 127, 145 

 period, North America in, 66 



Periodicity, 70, 75 



Periophthalmus, 120 



Permian period, 46, 76, 79, 111, 127 



period, aridity in, 145 



period, climate of, 51, 55, 127, 129, 



145 



Persia, 185 

 Peru, 180, 188, 189 

 Petromyzon, 116 

 Pfluger, E., 99 

 Phasic activity, 100 

 Phenacodus primavus, 136 

 Phosphates, 107 



Physical activity, optimum tempera- 

 ture for, 172 

 Pig, 177 

 Planetary nuclei, 19, 33 



system, 47 

 Planetesimal dust, 25 



hypothesis, 13, 101 



hypothesis, outstanding difficulties of, 

 20 



material, 32 

 Planetesimals, 35, 47 



earth-growth by slow accretion of, 



24 

 Planetoids, 4, 5, 26, 28 



earth-growth by rapid infall of, 25 



significance of, 26 

 Planets, 4, 5, 13, 18, 19, 24, 28, 31 



relations of, 5, 6 

 Plants, flowering, 65, 73 



herbaceous, 136 



lime-secreting, 113 

 Pleiades, 8 

 Pleistocene time, 46, 111, 138 



time, climate of, 55, 66, 110 

 Pliocene time, 46, 111 



time, aridity in, 143 

 Polypterus delhezi, 122 

 Positive areas, in earth's surface, 50 



areas, in North America, 62 

 Posture, erect, assumption of, 143 

 Primates, 136, 137, 143 



American, 137 



descent of, from trees, 143, 146 



