Auditory aperture or meatus: external --, crocodile, 250; dog, 402; turtle, 228; internal --, crocodile, 246, 251; dog, 392; turtle, 228 Auditory capsule, 20; cod, 96; crocodile, 250; dog, 390; dogfish, 74; frog, 156; newt, 143; turtle, 227 Auditory ossicles, crocodile, 251; dog, 393; duck, 320; mammals, 485 f.; turtle, 228 Auks, _42_; thoracic vertebrae, 332 Autostylic, 61, 119 Aves, _40_; characters, 295; see Birds Axial skeletal rods, 50 Axial skeleton, crocodile, 239; cod, 83; dog, 377; dogfish, 72; duck, 307; frog, 152; newt, 138; turtle, 218 Axis vertebra, crocodile, 241; dog, 380; duck, 309; turtle, 220 Axolotl, _35_; see _Siredon_ Aye Aye, _49_; see _Chiromys_ _Babirussa_, _45_; dental formula, 428 Baboon, _49_; see _Cynocephalus_ _Balanoglossus_, _30_, 50 _Balaena_, _44_, _357_; scapula, 495; _B. mysticetus_ baleen, 419 Balaenidae, _44_ Balaenoidea, _44_; general characters, 356 _Balaenoptera_, _44_, 357; manus, 506; thoracic vertebrae, 448; scapula, 495; _B. musculus_, cervical vertebrae, =444= Baleen, 3, 418 _Balistes_, _33_; teeth, 111 Balistidae, _33_ Ball and socket joints, 13 Bandicoot, _43_ Barb, 302 Barbule, 303 Barramunda, _34_; see _Ceratodus_ Basalia, dogfish, 79 Basibranchial, dogfish, 78; cod, 101; duck, 320; newt, 145; salmon, 95 Basi-branchiostegal, cod, 101; salmon, 95 Basicranial axis, 19; dog, 384 Basidorsalia, dogfish, 72 Basi-hyal, dogfish, 78; dog, 399; duck, 320 Basilar plate, 17 Basilingual plate, Anura, 180; crocodile, 259; frog, 161; turtle, 231 Basi-occipital, 19; crocodile, 246; cod, 97; dog, 386; duck, 315; salmon, 89; turtle, 224 Basipterygium, cod, 103; dogfish, 82 Basisphenoid, 19; crocodile, 247; dog, 386; salmon, 91; turtle, 225 Bastard wing, duck, 304 Bathyerginae, palate, 366 _Bathyergus_, _47_; auditory ossicles, 488; manus, 511 Batoidei, _32_, 64 _Batrachoseps_, _35_; teeth, 169 Bats, claws, 418; Horseshoe bats, _49_; see Chiroptera _Bdellostoma_, _31_, _55_; teeth, 57 Beak, 3; birds, 329; duck, 302; _Siren_, 168; tadpoles of Anura, 168; turtle, 215 Bears, _48_, _369_; manus, 511; pes, 526; sacral vertebrae, 452; skull, 479; Isabelline -- mandible, =438= Beaver, _47_; fibula, 520; humerus, 502; pes, 526; sacrum, 452; tail, 454