ODD-TOED UNGULATES 123 



(a) The movements of the jaws in mastication do not, however, 

 proceed in so pronounced a transverse direction as in the ox. 



(b) The distances between rows of molars above and below are nearly 

 equal. 



(c) and (d) The enamel folds of the molars do not run longitudinally, 

 but are undulating. 



(e) and (/) The size and number of the molars, and the shape of the 

 facial portion of the skull, are as in the ox. 



(g) The canines are small or entirely absent, especially in the female. 

 The large gap between the incisors (or canines) and molar teeth forms a 

 receptacle for the " bit." As a rule, only a slight pull or pressure is 

 sufficient (so sensitive are the lips) to direct the animal or to make it 

 start or stop. 



(h) The horse does not ruminate like the ox and its congeners. 



Other Equidae. 



The Ass (E. asinui). Apart from its smaller size, the colour of the 

 skin, length of the ears, and the presence of a hairy tuft on the tail, this 

 animal completely resembles the horse. It is very modest in its require- 

 ments, being even satisfied with thistles. Its obstinacy has become 

 proverbial. In the countries of the Mediterranean it is an indispensable 

 helpmate, especially in garden culture. The Mule is a hybrid between 

 the horse and the ass. It is of special importance in mountainous 

 countries, combining the strength of the horse with the endurance and 

 contentedness of the donkey. It strides securely along paths scarcely 

 passable by man, and with terrible abysses lying below. 



South and East Africa is the home of the striped and banded species 

 of Equus, the best known of which is the Zebra (E, zebra). Its 

 skin is white or light yellow, marked with black or brown transverse 

 stripes. A striking colour pattern like this may at first sight appear a 

 disadvantage to the animal by making its presence known to enemies at 

 a distance. On the other hand, in virtue of this colour an animal which 

 has become separated from the herd can descry its mates at a distance 

 and quickly rejoin them ; for these animals are so shy and cautious, and 

 so fleet of foot, that even a lion or tiger can do nothing against a herd 

 of them in the daytime. It is in the evening and on moonlight nights, 

 when they go to drink, that they are in danger of falling a prey to the 

 king of beasts lying in ambush for them. In the dim light, however, 

 the darker and lighter stripes of the skin so run into each other as to 

 make the animal appear gray and difficult to recognise even at a short 

 distance. Thus their striking colour markings at once render them 

 recognisable, and at the same time serve as a means of protection. 



