Hyporachis, 328 _Hypsilophodon_, _39_; predentary bone, 284 Hypsodont, defined, 345, 429 Hypural bone, cod, 85 Hyracidae, _47_ Hyracoidea, _47_; femur, 519; general characters, 362; manus, 510; nails, 418; skull, 472; teeth, 432 _Hyracotherium_, _46_; manus, 508; scapula, 496 _Hyrax_, _47_, _363_; see _Procavia_ Hystricidae, _47_ Hystricomorpha, _47_; auditory ossicles, 488 _Hystrix_, _47_; auditory ossicles, 488; see Porcupine Ichthyodorulites, 106 Ichthyoidea, _35_; general characters, 134 Ichthyopsida, _31_; general characters, 59 Ichthyopterygium, 130 _Ichthyornis_, _40_; mandible, 335; pelvis, 341; teeth, 330; vertebrae, 332 Ichthyornithiformes, _40_, 300 Ichthyosauria, _37_; general characters, 195; ribs, 285 Ichthyosauridae, _37_ _Ichthyosaurus_, _37_, _197_; limbs, 290; palatines, 281; pectoral girdle, 288; position of limbs, 28; skull, =196=; teeth, 273; vertebral column, 275 Ichthyotomi, _31_; general characters, 62; fins, 130 f.; tail, 116 _Iguana_, _38_; teeth, 273 Iguanidae, _38_; zygosphenes, 200, 276 _Iguanodon_, _39_, 208 f.; jaws, 292; predentary, 284; sternum, 288; teeth, 272 f.; vertebrae, 275 Iguanodontidae, _39_ Iliac surface of ilium, dog, 410 Ilium, 25; crocodile, 266; dog, 409; duck, 325; frog, 165; mammals, 513 f.; newt, 149; reptiles, 291; turtle, 235 Incisors, dog, 376 f.; mammals, 344 Incus, dog, 393; man, dog and rabbit, =485= Infra-marginal shield, turtle, 215 Infra-pharyngeal bone, cod, 101 _Inia_, _45_; cervical vertebrae, 444; lumbar vertebrae, 448 Innominate bone, dog, 409; mammals, 513 Insectivora, _48_; arm bones, 503; auditory ossicles, 488; cervical vertebrae, 446; general characters, 369 f.; manus, 512; pelvis, 515; pes, 527; sacrum, 452; shoulder-girdle, 499; skull, 480; sternum, 490; tail, 454; teeth, 440; thigh and shin, 520; thoraco-lumbar vertebrae, 450 Insectivora vera, _49_; general characters, 370 inter centra, 15; _Galeopithecus_, 370; Ichthyosauria, 195; Labyrinthodontia, 172; _Sphenodon_, 198; _Talpa_, 450 Interclavicle, 25; crocodile, 263; Monotremata, 494; reptiles, 289 Intercondylar notch, dog, 412 Intergular shield, turtle, 215 Interhyal, cod, 100 Intermedium, 27; see Carpus and Tarsus Intermuscular bones, cod, 86 Internasal septum, dogfish, 76