556 MANUAL OF ZOOLOGY. 



lates the number of the toes is even — either two or four — and 

 the third toe in each foot forms a symmetrical pair with the 

 fourth (Fig. 215, B, C). The dorso-lumbar vertebrae are nine- 

 teen in number, and there is no third trochanter on the femur. 

 If true horns are present, these are always in pairs, and. are 

 supported by a bony horn-core. The antlers of the Deer are 

 also paired, but they are not to be regarded as true horns. 

 The stomach is always more, or less complex, or is divided 

 into separate compartments, and the caecum is comparatively 

 small and simple. 



The section Artiodadyla comprises the Hippopotamus, the 

 Pigs, and the whole group of the Ruminants, including Oxen, 

 Sheep, Goats, Antelopes, Camels, Llamas, Giraffes, Deer, &c. 

 Besides these there is an extensive series of fossil forms com- 

 mencing in the Eocene or Lower Tertiary period, and in many 

 respects filling up the gaps between the living forms. 



OMNIVORA. 



1. HippopotamidcB. — This group contains only the single 

 genus Hippopotamus, characterised by the massive heavy l^pdy, 

 the short blunt muzzle, the large head, and the presence of 



2 — 2 

 teeth of three kinds in both jaws. The incisors are r^^, the 



canines extremely large, , and the molars, !——!- or -r— 7, 



■ " ' i^i' 7 — 7 6—6' 



with crowns adapted for grinding vegetable substances. The 

 upper canines are short, but the'lower canines are in the form 

 of enormous tusks, with a chisel-shaped edge. The feet are 

 massive, and are terminated by four hoofed toes each. The 

 eyes and ears are small, and the skin is extremely thick, and 

 is furnished with few hairs. The tail is very short. 



Several extinct species of Hippopotamus are known, but 

 there is only one well-established living form, the Hippopo- 

 tamus amphibius or River-horse, and this is confined to the 

 African continent. It is an enormously bulky and unwieldy 

 animal, reaching a length of eleven or twelve feet. It is noc- 

 turnal in its habits, living upon grass and small shrubs, and it 

 swims and dives with great facility. It is found in tolerable 

 abundance in the rivers of Abyssinia, and occurs plentifully 

 in South Africa. Another supposed species {H. Liberiensis) 

 occurs on the west coast of Africa, but there is some doubt as 

 to the specific distinctness of this. 



2. Suida. — The group of the Suida, comprising the Pigs, 

 Hogs, and Peccaries, is very closely allied to the preceding ; 



