horses, asses, rhinoceroses, and tapirs.

Contrasted with these, _Artiodactyla_ have always an even number of
functional digits, the third and fourth reaching the ground
symmetrically, bearing the weight and forming the "split hoof;" the
second and fifth remain, in most cases, as mere vestiges, showing
externally as the accessory hoofs or dewclaws; in the hippopotamus alone
they are fully developed and the animal has a four-toed foot. In deer
and bovine animals the incisors and frequently the canines have
disappeared from the upper jaw, and the molars are unlike the premolars
in having two lobes instead of one. The stomach is always more or less
complex; at its extreme reaching the ruminant type with four
compartments, in association with which is a caecum reduced in size and
simple in form. Nearly all have horns or antlers, at least in one sex.

Most split-hoofed animals are ruminants, but there is a small remnant,
probably of early types, which are not. The present ungulates may be
summed up in this way:

Odd-toed: _(Perissodactyla)_--
Horse,
Ass,
Rhinoceros,
Tapir.

Even-toed: _(Artiodactyla)_--

Non-ruminants--
Hippopotamus,
Swine,