324 VERTEBRATE ANIMALS. 
one is always placed behind the other in the middle line of the 
head, and the hinder one is much the shortest. The various 
species of Rhinoceros are found in India, Java, Sumatra, and 
Africa, inhabiting marshy places and feeding chiefly on the 
foliage of trees. The Zafzrs have four toes to each of the fore- 
legs, but only ¢irvee toes on the hind-legs, so that they are pro- 
perly odd-toed, The nose forms a short movable proboscis, 
used in stripping off the leaves of trees. They are large clumsy 
animals, which inhabit South America, Sumatra, and Malacca. 
The third and last family of the Perzssodactyla is that of the 
Egquide, comprising the Horse, Ass, Zebra, and Quagga. In 
this family the toes are reduced to ove to each foot, enclosed in 
a single broad hoof, without any supplementary hoofs. There 
is a continuous series of incisor teeth in both jaws, and in the 
males canines are present. The dental formula is— 
a pe=sr] —f bide aes 
ee (or none); pm 373 ; 33 = 40. 
aa en Sian oo 
All the varieties of Horses appear to be descended from the 
single species Lguus caballus, which seems to have been primi- 
tively a native of Central Asia. When the American Continent 
was discovered it certainly possessed no living horse, but the 
horse has now become completely naturalised there, and we 
know that America formerly possessed about twenty species of 
horses, all of which are now extinct. In the genus Aszzus are 
the Asses, Zebras, and Quaggas. The wild Ass is a native of 
Asia, and the domestic Ass is probably descended from it. The 
Zebras and Quaggas are exclusively African, and are distin- 
guished by their beautifully-striped and banded bodies. 
The Artiodactyles or Even-toed Ungulates are divided into 
two groups,— 
1. Omnivora, as the Pig and Hippopotamus. 
2. Ruminantia, which chew the cud, such as Oxen, Deer, 
Camels, &c. 
Of the Omnzvorous forms, the Hippopotamus is characterised 
by its massive heavy body, short blunt muzzle, and feet with 
four hoofed toes each. The Hippopotamus is found in the 
rivers of Abyssinia, and throughout the whole of Africa to the 
south of this. It reaches a length of from eleven to twelve feet, 
is nocturnal in its habits, and swims and dives with great facility. 
The Pigs, Peccaries, and Wart-hogs constitute the family Suzda, 
