22 



TUSKS AND THEIR USES. 



described many years ago by Sir R. Owen, under the 

 name of Dicynodon, are thus armed. In these reptiles, 

 some of which attained gigantic dimensions, the jaws were 

 mainly sheathed in horn like those of a turtle ; the single 



pair of tusks curving down- 

 wards and forwards from 

 near the middle of the upper 

 one. Possibly these tusks 

 were capable of being em- 

 ployed when the mouth was 

 open like those of lions or 

 tigers ; but otherwise it is 

 difficult to see their use. 

 Certain allied reptiles from 

 the aforesaid formations, 

 known as anomodonts, 

 had a full series of teeth, 

 with a large paii of tusks 

 in the upper jaw, which 

 may or may not have been 

 rooted, but are exceedingly 

 like those of certain car- 

 PIG. 11. Extremity of the Skull nivores. As these reptiles 

 and Tusk of a Uintathere. are not the direct ancestors 



of mammals, we have 



thus evidence of the acquisition of tusks in two distinct 

 classes. 



As regards solid tusks, or those in which the lower end 

 is closed at a certain period coincident with the cessation 

 of growth, almost the only mammals, save the rhinoceroses 

 (where, as we have seen, there may be a f orwardly-directed 

 pair in the lower jaw) and some of the marsupials, in 

 which they attain any marked development are the carni- 

 vores. Among these, the maximum size of tusks at the 

 present day is attained in the larger felines, such as the 

 lion, tiger, and leopard. In these animals the tusks are, 

 however, never so much elongated as to bar the front of 

 the open mouth ; while very frequently their tearing 

 power is increased by the hinder cutting-edge being 

 finely serrated. Their terrible effect in tearing and 



