200 ANIMALS OF THE PAST 



from the jaw are bent directly downwards. 

 No perfect skull of this creature has yet been 

 found, but it is believed to have had a short 

 trunk. For a long time nothing but the skull 

 was known, and some naturalists thought the 

 animal to have been a gigantic manatee, or sea 

 cow, and that the tusks were used for tearing 

 food from the bottom of rivers and for anchor- 

 ing the animal to the bank, just as the walrus 

 uses his tusks for digging clams and climbing 

 out upon the ice. In the first restorations of 

 Dinotherium it is represented lying amidst 

 reeds, the feet concealed from view, the head 

 alone visible, but now it is pictured as stand- 

 ing erect, for the discovery of massive leg- 

 bones has definitely settled the question as to 

 whether it did or did not have limbs. 



There is another hint of relationship in the 

 upper tusks of the earlier mastodons, and this 

 is the presence of a band of enamel running 

 down each tusk. In all gnawing animals the 

 front, cutting teeth are formed of soft dentine, 

 or ivory, faced with a plate of enamel, just as 

 the blade of a chisel or plane is formed of a 

 plate of tempered steel backed with soft iron ; 



