Formation 155 Distribution and Classification 157 Tortoises 158 Land 158 Margined 159 Moorish 159 Greek 160 Elephantine 160 Genus Pyxis 161 Ditto Kinixys 161 Homopodes 161 _Elodians, or Marsh Tortoises_: Mud 162 Emydes 163 Pleuroderes 164 _Potamians, or River Tortoises_: Trionyx 164 _Thalassians, or Sea Tortoises_: Green 177 Hawk's-bill 177 Loggerhead 178 Leather-back 178 BIRDS. INTRODUCTORY CHAPTER. Anatomy 181 Plumage 184 Beaks 189 Digestive Organs 191 Powers of Sight 193 Vocal Organs 195 Nests 197 Reproduction 201 Longevity 203 Utility 205 Classification 207 CHAPTER I. THE NATATORES, OR SWIMMING BIRDS. Divers 212 Great Northern 213 Imbrine 216 Arctic 216 Black-throated 216 Red-throated 217 Penguins 218 Manchots 219 Grebes 221 Castanean 222 Crested 223 Guillemots 224 Chapter II. DUCKS, GEESE, SWANS, AND PELICANS.