The classification of the living Artiodactyla is a comparatively simple matter. They are divided into Bunodonta, including three families—pigs, peccaries, and hippopotami—and Selenodonta, or Ruminants, including all the rest. The modern selenodonts in turn are divided into Tylopoda, or camels; Tragulina, or chevrotains; and Pecora, the deer-antelope-cattle group. The characters of these groups are sharply marked in teeth and feet as well as in various features of the soft anatomy. The bunodonts all have in common round-cusped crushing teeth, powerful canine tusks of triangular form, four-toed feet with the metapodials more or less completely separate, simple stomach, and various other features of the soft anatomy. The selenodonts all have crescentic cusps on molars and premolars, the molars quadrate with four cusps, the premolars with two, the upper incisors reduced or missing, lower incisors and usually the canine small, procumbent, spatulate, the feet two-toed with the middle pair of . . .