44 ANIMAL SKETCHES. CHAP. 



and the deer. Like these animals the giraffe has horns ; 

 but they differ from the horns of cattle and the antlers of 

 deer, for they consist of bony cores covered with hairy 

 skin with a tuft of stiff bristles. In old giraffes there is 

 also a prominent projection in the middle of the forehead 

 looking somewhat like a third horn. 



Notwithstanding certain marked peculiarities in the 

 tooth arrangement in the hippopotamus and the giraffe, 

 the ungainly tusks of the former, and the absence of 

 upper front teeth in the latter, both these animals, like us, 

 have two sets of teeth the baby-set of milk teeth, and the 

 larger and fuller series of permanent teeth. And these 

 permanent teeth come up from below to displace their 

 smaller precursors, except the hinder cheek-teeth, which, 

 like our larger molars and wisdom teeth, have no milk 

 predecessors. But when we come to the elephant's teeth, 

 we find some of the most marked peculiarities which are 

 exhibited by any members of the animal kingdoms. 



Most striking perhaps are the long, curved tusks, which 

 continue to grow throughout life. They are incisors. 

 All the other front teeth and the canines are non-existent 

 in the elephant's upper jaw, and there are no front teeth 

 or canines in the lower jaw of the existing elephants, 

 though a fossil elephant, the mastodon, had long incisor 

 tusks in the lower jaw. The tusks of the elephant are 

 the only teeth which in this animal have milk pre- 

 cursors or baby teeth in the ordinary way. 



If you examine the cheek-teeth of an elephant, in the 

 skulls for example in the Natural History Museum, you 

 will find that they are few in number but of great size. 

 Their worn surfaces show the eroded summits of a number 

 of ridges running across the tooth, each with a shallow 

 valley at the top, and separated from the neighbouring 

 ridge by a deeper valley- trench. In the tooth which lies 



