330 BACKBONED ANIMALS. 
however, under the skin, that tell an interesting story in 
the ancestry of the family.* The domestic horse (£ 
caballus) came originally from the Old World, and is not 
found now in the wild state except where it has been re- 
leased by man, as the mustang of South America and the 
muzir of Tartary. 
Ponies are dwarf horses, produced in cool countries, 
as Shetland. The wild ass (Z. ovager) ranges in herds 
from the Indies to Mesopotamia. They are distinguished 
by long ears, the tail ending in a tuft. The hinny and 
mule are hybrids of the ass (4. asimus) and a horse. Four 
species of zebra are known in Asia and Africa. They are 
striped transversely with dark and white bands. The 
voice of the quagga of Africa resembles the bark of a dog. 
‘The onagga of Africa is smaller than the ass. They are 
dark bay with black stripes, the tail and legs being white. 
The peculiar marking is protective. 
VALUE.—Horses, mules, asses, etc., are the most valuable of do- 
mestic animals ; almost every part of the animal is valued in trade. 
* Professors Marsh and Huxley, especially the former, have made 
interesting discoveries concerning the fossil horse, and its ancestry is 
more complete than that of any other animal. The remains are found 
in the Tertiary beds of North America. The earliest horse was the 
eohippus (Eocene time), as large as a fox. The following is the gene- 
alogy of the horse : 
Period In Front Hind No.of In 
SHOT: America. Toes. Toes. Teeth. Europe. 
Recent. . 2. 6. — I r Equus. 
; an : ; 40 
: Upper Pliocene . Equus 2splints 2 splints Equus. 
er I I 
6. Upper Pliocene. . Pliohippus asplints 2 splints 42 ~ 
; i large 1 large 7 ‘ 
5. Lower Pliocene. . Protohippus asmall asmall “4 Hipparion, 
4. Upper Miocene . . Miohippus 3 3 44 Anchitherium. 
‘ ; _3 = 
3. Lower Miocene. . Mesohippus Y splint 3 44 
z Upper Eocene . . Orohippus 4 3 44 _ 
1. Lower Eocene . . Eohippus # 3 44 _ 
1 splint 
