
INDEX. 
Polycotylus, 854 
Polypora, 723 
_ Polypterus, 710 
Polypiychodon, 809 
Polyzoan Limestone, 723 
Pomerania, dunes of, 324 
Pompeii, destruction of, 216 
Ponce, 142 
Poplars, fossil, 803, 839, 868, 877 
Populus, 859, 862 
Porambonites, 665, 669* 
Porcellia, 697 
Porcupine, during Glacial Period, 891 
Porosity of rocks, 299, 346 
Porphyrite, 144 
Porphyritic structure, 90 
Porphyroid, 128 
Porphyry (quartz), 135; quartzless, 158 
Portage Group, 704 
Portland Oolites (Portlandian), 794, 797 
Posidonia, 737, 748, 776* 
Posidonomya, 737, 748 
Post-Pliocene deposits, 883 
Post-Tertiary Formations, 883 
Potamaclis, 857 
Potamides, 850, 855* 
Potamogeton, 862 
Potamomya, 857 
Potassium in minerals and rocks, 59 
Potassium Iodide, in petrographical ana- 
lysis, 193 
Poteriocrinus, 722 
Pothocites, 732 
Pot-holes, 373, 415 
Potsdam Formation, 660 
Potstone, 120 
Prairie-dog, geological action of, 455 
Prearcturus, 712 
Pre-Cambrian (see Archean) 
Precession of the equinoxes, geological 
effects of, 14, 29 
Predazzo, local metamorphism at, 578 
Pre-glacial land-surfaces, 884 
Prehistoric periods in geology, 902 
Prepecopteris, 734 
Present, explains the past in geology, 3 
- Pressure, influence of in fusion, 297; in- 
creases solvent power of water, 300, 312, 
348: effects of on rocks, 44, 309 
Prestwichia, 724 
Primitia, 664, 669 
Primordial zone, 653, 657, 659, 689 
Prionocyclas, 832 
Prismatic structure, 504, 506, 573; produc- 
tion of, 292 
Pristis, 840 
Proboscideans, chief era of, 863 
Procamelus, 881 
Productus, 696, 723*, 752* 
Proétus, 676 
Promephitis, 878 
Propora, 688 
Propylite, 144 
Protachillewm, 663 
961 
Protaster, 664 
Proteacex, 803, 838, 855 
Protemys, 807 
Proterosaurus, 754 
- Protocystites, 650* 
Protogine, 134 
Protohippus, 881 
Protolycosa, 732 
Protomeryz, 869 
Protopteris, 752 
Protospongia, 650* 
Prototaxites, 708 
Protozoa as fossils, 611 
Protriton, 754 
Proviverra, 840 
Psammites, 154 
Psammitic structure, 87 
Psammobia, 848, 858, 867 
Psammodus, 724 
Psaronius, 708, 752 . 
Pseudalerus, 880 
Pseudocrinites, 678 
Pseudodiadema, 773, 820 
Pseudoliva, 840 
Pseudomorphs, 61, 83; in relation to 
alteration of rocks, 352 
Pseudosigillaria, 734. 
Psilocephalus, 655 
Psilophyton, 705, 708* 
Pteranodonts, 811 
Pteraspis, 666, 710 
Pterichthys, 698, 710* 
Pterinea, 665, 696 
Pteroceras, 799, 819 
Pterocerian group, 797, 799 
Pterodactylus, 778, 782*, 808 
Pterodon, 840 
Pterophyllum, 761, 772, 828 
Pteroplax, 733 
Pierosaurians, or winged reptiles, 778, 
808 
Pterotheca, 666 
Pterozamites, 761, 772 
Pterygotus, 664, 697*, 711, 714 
Ptilodictya, 665 
Ptychaspis, 660 
Ptychoceras, 807 
Ptychodus, 807 
Ptychophyilum, 664, 677* 
Ptychopyge, 687 
Puddingstone, 156 
Pullastra, 762* 
Pulverization as a part of petrographical 
analysis, 93, 191 
Pulvulina, 795 
Pumice, 89, 142; drift of on the ocean, 
436 
Pumiceous structure, 89 
Pupa, 732, 866, 898 
Purbeck Beds, 783, 794, 796, 797 
Purpura, 774, 873 
Pycnodus, 775, 807 
Pygaster, 773 
~ 
Pygopterus, 753 
