Interorbital septum, birds, 333; crocodile, 247; duck, 317; reptiles, 277 Interspinous bones, cod, 86 Intertarsal ankle joint, 190 Intervertebral discs, 15, 378 Ischial tuberosity, dog, 411 Ischium, 25; crocodile, 266; dog, 410; duck, 325; frog, 165; newt, 149; turtle, 235 _Ischyodus_, _32_, _66_ Ivory, 5 Jacana, _42_; see _Parra_ _Jacare_, _39_; scutes, 271 Jaws, 21; cod, 98 f.; crocodile, 252 f.; dog, 395 f.; dogfish, 77; duck, 317 f.; frog, 158 f.; newt, 143 f.; salmon, 93 f.; turtle, 229 f. Jerboa, _47_; cervical vertebrae, 446; pes, 526 Joints, kinds of, 13 Jugal, 22; crocodile, 255; dog, 398; duck, 318; turtle, 229 Jugulares, 132 Kangaroo, _43_; dental formula, 423; lumbar vertebrae, 447; pectineal process, 513; pes, 522; tail, 453; teeth, 345 Kestrel, claws, 330 Killer, _45_; see _Orca_ Kiwi, _40_; see _Apteryx_ Knee-cap, see patella Koala, _43_; lumbar vertebrae, 447; pes, 522; tail, 453 Kükenthal, W., on teeth of Cetacea, 426; on teeth of Marsupials, 422 Labial cartilage, dogfish, 77; _Squatina_, 119 Labridae, _33_ _Labrus_, _33_; see Wrasse Labyrinthodontia, _35_; buckler, 168; general characters, 135; interparietal foramen, 173; pelvis, 187; ribs, 182; skull, 176; teeth, 169 Lacertilia, _37_; general characters, 199; pectoral girdle, 288; skull, 277; vertebrae, 275 Lachrymal, 20; cod, 97; crocodile, 251; dog, 394; duck, 317; salmon, 93 Lacunae, 10 _Lagenorhynchus_, _45_; skull, 462 _Lagostomus_, _47_; maxillae, 477 Lambdoidal crest, duck, 315 Lamella of malleus, dog, 393 Lamnidae, _32_ Lamprey, _31_, 55 f. Lancelet, _30_; see _Amphioxus_ Laridae, _42_; see Gulls Larks, _42_ Larvacea, _30_; notochord, 51 _Latax_, _48_; pes, 526 Lateral ethmoid, 21; cod, 97; salmon, 89 f. Leathery turtle, _37_; see _Dermochelys_ Lemuroidea, _49_; caudal vertebrae, 454; general characters, 372; nails, 418; ribs, 493; sacrum, 452; skull, 482; thoraco-lumbar vertebrae, 450; see Lemurs Lemurs, carpus, 512; pes, 527; teeth, 441; see Lemuroidea Lenticular, 485; dog, 393 _Lepidosiren_, _34_, _70_; branchial arches, 125; fins, 130 Lepidosteidae, _33_ _Lepidosteus_, _33_; attachment of teeth, 108; distribution, 66; pectoral fins, 131; scales, 67, 104; skull, 123; tail, 117; vertebrae, 68