Heterostraci, _31_; general character, 54 _Hexanchus_, _31_; branchial arches, 63, 121 Hinge joint, 13 _Hipparion_, _46_; manus, 508; pes, =524= Hippopotamidae, _45_ _Hippopotamus_, _45_, _359_; dental formula, 427; hair, 416; mandible, 467; manus, 506; pes, 523; scapula, 496; skull, 467; teeth, 345 Hoatzin, _41_; see _Opisthocomus_ Holocephali, _32_, 65, 104; clasper, 132; spinal column, 113; tail, 116; teeth, 109 Holoptychiidae, _33_ _Holoptychius_, _33_; scales, 105 Holostei, _33_; general characters, 68; teeth, 110; see Bony Ganoids Hominidae, _49_, _373_ _Homo_, _49_; see Man Homocercal tail, 60, 69, 117; codfish, 87 Homodont, defined, 7 Hoofs, 3, 418 Hoopoe, _42_, 335 _Hoplopterus_, spur, 330 Hornbill, _42_, 331; bony crest, 334; interorbital septum, 333 Horns, 3, 417 Horny plates on palate, 418; -- teeth, Lampreys, 4; Myxinoids, 57; _Ornithorhynchus_, 4 Horse, _46_, _360_; fibula, 519; malleus, 487; manus, 507; pes, =524=; skull, 471; teeth, 345, 430; ulna, 501 Howling monkey, _49_; see _Mycetes_ Humerals, duck, 303 f. Humeral shield, turtle, 215 Humerus, 26; crocodile, 263; dog, 405; duck, 323; frog, 164; newt, 147; turtle, 232; wombat, =500= Humming-birds, _42_, 335 Humpbacked whale, _44_, _357_ _Hyaena_, _48_, _369_; hallux, 526; pollex, 511; sacral vertebrae, 452; teeth, 437 Hyaenidae, _48_; humerus, 502 _Hyaenodon_, _48_, _368_ Hyaenodontidae, _48_ Hyaline cartilage, 10 _Hydrochaerus_, _48_; teeth, 437; see Capybara _Hydromys_, _47_; dental formula, 436 Hydrophidae, _38_; scales, 270 _Hydropotes_, _46_; canines, 429 _Hyla_, _36_; fronto-parietal fontanelle, 179; sternum, 184 Hylidae, _36_ _Hylobates_, _49_; ribs, 493; skull, 482 Hyoid, 21; alligator, =285=; Amphibia, 180; birds, 336; cod, 100; crocodile, 259; dogfish, 77; dog, 399; duck, 320; frog, 161; newt, 144; reptiles, 284; salmon, 94; turtle, 231, =285= Hyomandibular, 23; cod, 100; dogfish, 78; salmon, 94 _Hyomoschus_, _45_ Hyoplastron, turtle, 217 Hyostylic, 61, 119 _Hyotherium_, _45_; teeth, 427 _Hyperodapedon_, _37_, _198_; premaxillae, 284 _Hyperoödon_, _44_; skull, 464; sternum, 489; thoracic vertebrae, 448 Hypo-branchial, cod, 101; dogfish, 78 Hypo-hyal, cod, 100; salmon, 95 Hypo-ischium, Lacertilia, 292 Hypoplastron, turtle, 217