OCTOPODA, 205 _Octopus_, 205 _Odontaspis_, 269, 270, 271 ODONTOCETI, 295 _Odontopleura_, 229, 231 _Odostomia_, 198, 200 _Oenonites_, 153 _Olenellus_, 226, 227 _Oliva_, 204 _Ommatocarcinus_, 247 _Omphalotrochus_, 194 Oolitic ironstone, 81 _Ophileta_, 192, 193 OPHIUROIDEA, 141 _Orbiculoidea_, 160 _Orbitoides_, 99 Ordovician bivalve, 177 " brachiopods, 159 " cephalopods, 205 " corals, 113 " crinoids, 135 " gasteropods, 193 " Phyllocarida, 244 " Radiolaria, 102 " sponges, 108 " trilobites, 227 _Ornithorhynchus_, 286, 287 _Orthis_, 159, 160, 161, 162 " limestone, 74 _Orthoceras_, 204, 205, 206, 207, 208 _Orthonota_, 177 _Orthothetes_, 162 OSTRACODA, features of carapace, 234 " habits of, 234 " structure of, 233 _Ostrea_, 182, 184, 187 _Otaria_, 299 _Oxyrhina_, 269, 270, 271 OXYSTOMATA, 247 _Oxytelus_, 250 _Pachydomus_, 181 _Pachyornis_, 282, 283 _Pachypora_, 73, 116 _Palaeaster_, 140, 141 _Palaeeudyptes_, 280, 281 _Palaeohatteria_, 276 _Palaeolycus_, 250 _Palaeoneilo_, 177, 178 _Palaeoniscus_, 261, 263, 274 _Palaeopelargus_, 283 Palaeozoic chitons, 189 " Cladophora, 122 " Cryptostomata, 156 " errant worms, 153 " strata, 47 " Trepostomata, 155 _Palissya_, 89, 164 _Pallymnarchus_, 279 _Palorchestes_, 290 _Panda_, 203 _Panenka_, 177 _Paracyainus_, 118 _Paracyclas_, 177, 179 _Paradoxechinus_, 145 _Paradoxorhyncha_, 239 _Parasqualodon_, 295, 296 _Pareiasaurus_, 276 _Patella_, 190, 191 _Pecten_, 175, 182, 183, 184, 185, 186, 187, 188 PELECYPODA, characters of, 174 " hinge structure of, 175 Pelican, 283 _Pelicanus_, 283 _Pelosina_, 97 _?Peltopleurus_, 262 _Pentacrinus_, 137, 138 _Pentagonaster_, 141 _Pentamerus_, 160, 162 _Penteune_, 91 _Peragale_, 289 _Perameles_, 289, 295 _Perisphinctes_, 209 Permian and Triassic reptiles, 276 _Perna_, 187 _Peronella_, 148 _Persoonia_, 90 _Petaurus_, 295 _Petraia_, 113 _Phacops_, 229, 230, 231 Phalanger, 295 _Phanerotrema_, 194 _Phascolomys_, 289, 295 _Phascolonus_, 289 _Phialocrinus_, 137 _Phillipsia_, 232 _Phoenicopsis_, 88 _Pholas_, 177 _Pholidophorus_, 262, 263 _Phos_, 198 _Phragmoceras_, 207 _Phryganea_, 75 PHYLACTOLAEMATA, 155 PHYLLOCARIDA, structure of, 243 _Phyllocladus_, 90 _Phyllograptus_, 123, 126 PHYLLOPODA, 233 _Phyllotheca_, 274 _Physa_, 191 _Physonemus_, 261 Pigeon, 283 _Pinna_, 186 PINNIPEDIA, 299 _Pisania_, 202 _?Pisocrinus_, 136 _Placopsilina_, 97 _Placotrochus_, 118 _Placunanomia_, 184, 187 _Plagiarca_, 184 _Plagiaulax_, 286 _Planorbis_, 191 Plants, fossil, 66 Plant series, characters of, 39 _Platalea_, 283 _Platyceps_, 273 _Platyceras_, 192, 194, 195, 196 _Platycoila_, 91 _Platycrinus_, 137 _Platyschisma_, 196