All the species of _Ancistrodon_, so far as they have been observed, are in the habit of raising and vibrating the tail, like the Rattlesnakes, when coiling themselves up in a defensive attitude. INDEX Acanthocephala, 110 _Acrochordinæ_, 5 Adder, 230 Æsculapian Snake, 187 _æsculapii_ (_Coluber_), 187 _Aglypha_, 4, 151 _Ailurophis vivax_, 217 Albinism, 39 Aldrovandi's Snake, 182 Altitudinal range, 118, 123 _Amblycephalidæ_, 5 _ammodytes_ (_Vipera_), 249 Anal pockets, 83 Anal shield, 17 _Ancistrodon_, 261 _Ancistrodon halys_, 262 Antitoxic serums, 66 Apical pits, 15, 75 Arteries, 77 Ascariasis, 111 _asianus_ (_Zamenis gemonensis_, var.), 173 Asp Viper, 239 _aspis_ (_Vipera_), 239 _astreptophorus_ (_Tropidonotus natrix_, var.), 154 _ater_ (_Tropidonotus natrix_, var.), 156 _atrovirens_ (_Coluber_), 170 _aurolineatus_ (_Coluber_), 167 _austriaca_ (_Coronella_), 197 Bacteria, 113 _berus_ (_Pelias_), 221 _berus_ (_Vipera_), 230 Bezoar stones, 141 _bilineatus_ (_Tropidonotus natrix_, var.), 154 Blind Snake, 144 Blood-supply, 77 Blunt-nosed Viper, 257 Body, 8 _Boidæ_, 4, 146 _Boinæ_, 4, 146 _bosniensis_ (_Vipera berus_, var.), 236 Brain, 73 Burrowing Snakes, 91 _cæruleus_ (_Coluber_), 233 Canker, 113 Canthus rostralis, 13 Captivity, 100 _carbonarius_ (_Zamenis_), 172 _caspius_ (_Zamenis gemonensis_, var.), 172 Cat-Snake, 217 Caucasian Cat-Snake, 219 _cervone_ (_Elaphis_), 182 Cestoda, 112 _cettii_ (_Tropidonotus natrix_, var.), 155 _chersoides_ (_Tropidonotus_), 167 Classification, 2 Cobra di capello, 9 _Coelopeltis_, 207 _Coelopeltis monspessulana_, 208 _collaris_ (_Contia_), 207 Coloration, 29 Colour, 29 _Coluber_, 181 _Coluber æsculapii_, 187 _Coluber atrovirens_, 170 _Coluber aurolineatus_, 167 _Coluber cæruleus_, 233 _Coluber dione_, 185 _Coluber dumfriesiensis_, 200 _Coluber flavescens_, 187 _Coluber hydrus_, 160 _Coluber insignitus_, 208 _Coluber leopardinus_, 191 _Coluber longissimus_, 187 _Coluber quadrilineatus_, 191 _Coluber quatuorradiatus_, 182 _Coluber quatuorlineatus_, 182 _Coluber riccioli_, 202 _Coluber rubens_, 204 _Coluber sauromates_, 183 _Coluber scalaris_, 194 _Coluber torquatus_, 152 _Coluber viridiflavus_, 170 _Colubridæ_, 4, 150 _Colubrinæ_, 4, 151 _concolor_ (_Tropidonotus tessellatus_, var.), 162 _concolor_ (_Vipera berus_, var.), 234 _Coniophis_, 7 Constriction, 96