MAMMALIA 107 



The domesticated Horse {Equus caballus) has such a long 

 history of captivity that its ancestry is obscure, and it is by no 

 means certain that all horses have descended from one stock. 

 It is, however, generally believed that one original stock was 

 Asiatic, and perhaps the Tarpan or Wild Horse {Equus tarpan) 

 of Central Asia comes nearest to this stock, though even that is 

 far from being certain. Wild Asses are found both in Africa and 

 Asia, and the domesticated form familiar to us comes nearest 

 to an Asiatic species, the Onager {Equus onager), which ranges 

 from Asia Minor to India. The domestic asses of Egypt and 

 Abyssinia, however, more closely resemble the African Wild Ass 

 {Equus tcBniopus\ native to the region between the Red Sea and 

 Nile. The remaining living equines are those striped African 

 species known as Zebras or Tiger Horses. The kind most 

 commonly seen in zoological gardens is Burchell's Zebra {Equus 

 Burckelli), herds of which are still to be found in the grassy 

 plains to the north of the Orange River. 



II. Even -TOED Ungulates (Artiodactyla). — This large and 

 important group of Ungulates includes not only many valuable 

 domesticated forms, such as swine, oxen, goats, sheep, and camels, 

 but such familiar types as hippopotamus, antelopes, llama, and 

 giraffe. The even number of the toes is a character of far less 

 importance than the symmetry of the foot, there being no single 

 digit which is symmetrical in itself, like the third or middle one 

 in the preceding group. 



Two sections are recognized: — A. Non-ruminating forms; and 

 B. Ruminants. 



A. Non- Ruminating Forms 



This includes: i. the Hippopotamus Family, and 2. the Pig 

 Family, in neither of which are the digestive organs modified for 

 the purpose of ruminating or " chewing the cud ". They belong, 

 therefore, to the "unclean animals" of the Levitical law, despite 

 their cloven feet (Lev. xi). 



■ I. The Hippopotamus Family is entirely confined to the rivers 

 of Africa, with the adjacent swampy ground, and is represented by 

 two living species, i.e. the small Liberian Hippopotamus {Hippo- 

 potamus Liberiensis), limited, so far as known, to Liberia, and the 

 Common Hippopotamus {H. amphibius), the large form frequendy 

 seen in captivity, which has a much wider range. The appearance 



