ANCESTORS OF MAMMALS 



25 



former days the mastodons were particularly interesting, 

 being giant elephants with from one to four tusks. Mas- 

 todon turiensis, of the Pliocene time, had two tusks in the 

 upper jaw, straight, turning toward each other at the 

 points. In M. oJiiotecus the tusks tipped up gradually in 

 a graceful curve; and in the lower jaw was a single tusk, 

 so that the animal was a three-tusker. In M. longirostris 

 there were, besides two long upper tusks, two short sharp 

 ones in the lower jaw — a formidable defense. Four spe- 

 cies of these huge creatures formerly roamed America, 

 besides an elephant proper, and the mammoth. Five 

 species have been found in India, and two or three in 

 England. With these large elephants were pygmies, ani- 

 mals not larger than the common sheep. 



Larger than the elephants was the Dinotherium (Fig. 1 7), 

 a huge elephantine animal with a proboscis and two large 

 tusks, calling to mind those of 

 the walrus, inasmuch as they 

 turned down and in toward the 

 body, and doubtless could be 

 used by the animal in pulling 

 down limbs or even hauling it- 

 self up a steep bank from the 

 water, in which it is supposed 

 to have been as much at home 

 as the hippopotamus. 



Besides these strange forms 

 there were countless others, 

 large and small, that must have roamed the world in this 

 age — the forerunners of the mammals of to-day. Herds 

 of horses (Hipparion) galloped over the plains ; the fierce, 



Fig. 17. — Skull of the 

 Dinotherium. 



