TUSKS OF ELEPHANTS. 



17 



In both species of existing elephants, as in many of the 

 mastodons (Fig. 7), only the upper pair of tusks is thus 

 developed; but in other mastodons these organs were 

 present in both jaws, the upper pair being, however, 

 always much larger than the lower. In the pigs and 

 babirusa the_ tusks, of which the upper pair are implanted 

 in the true jaw-bone, correspond severally with those of 



Fig. 8. — li'oru part of >Sku]l and Tusks of Eabirusa. 



the lion and the wolf, and are accordingly reckoned as 

 canines. This, however, is not the case with those of the 

 elephants and mastodons, which grow in great jJart from 

 the pre-maxillary bone, and thus correspond with one 

 pair of the front or incisor teeth of other mammals. 

 Consequently, much as they resemble them in general 

 appearance, the tusks of an elephant are not homologous 

 with those of a pig or a babirusa. As we have entered 



