160 



ANIMALS OF THE PAST 



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 anchoring 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 standing erect, 

 for the discovery of massive leg-bones has definitely 

 settled the question as to whether it did or did not have 

 limbs. 



Tooth of Mastodon and Mammoth 



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; the object of this 

 being the same in both tooth and chisel, to keep the 

 edge sharp by wearing away the softer material. In 

 the case of the chisel this is done by a man with a grind- 

 stone, but with the tooth it is performed automatically 

 and more pleasantly , by the gnawing of food. In the 



