TEETH OF UNGULATA. 345 



having a depression on its inner surface, and each fang begins to 

 be subdivided. The third, p 3, has a similar but broader crown 

 implanted by four fangs. The fourth, p 4, has two principal 

 tubercles and some irregular vertical pits on the inner half of the 

 crown. The first true molar, m i, when the permanent dentition 

 is completed, exhibits the effects of its early development in a 

 more marked degree than in most other mammals, and in the 

 Wild Boar has its tubercles worn down, and a smooth field of 

 dentine exposed by the time the last molar has come into place ; 

 it originally bears four primary cones, with smaller subdivisions 

 formed by the wrinkled enamel, and an anterior and posterior 

 ridge. The four cones produced by the crucial impression, of 

 which the transverse part is the deepest, are repeated on the 

 second true molar m 2, with more complex shallow divisions, and 

 a larger tuberculate posterior ridge. The greater extent of the 

 last molar, m 3, is chiefly produced by the development of the 

 back ridge into a cluster of tubercles ; the four primary cones 

 beinsf distinguishable on the anterior 



2 1 4 



main body of the tooth. The crowns 

 of the lower molars are very similar 

 to those above but are rather nar- 

 rower, and the outer and inner basal 

 tubercles are much smaller, or are 

 wanting ; the grinding surface of the 



i i r> 0*7/1 Grinding surface, (TO 3) fite. 



last is shown in ng. 2/4. 



The first or deciduous dentition of the Hog consists of 







The canines are feeble, and have their normal direction in both 

 jaws, the upper ones descending according to the general type, 

 which is not departed from until at a later period of life. The first 

 deciduous molar is not succeeded by a premolar, but holds the 

 place of such some time after the other deciduous molars are shed. 

 The dentition of the Wart-hogs is reduced by the suppression 

 of certain incisors and of the first two premolars the tooth- 

 forming energy being, as it were, transferred to the last true 

 molar, fig. 275, m 3, wiiich is even more remarkable than in the 

 common hog for its size and complexity in both jaws : it is per- 

 haps the most peculiar and complex tooth in the whole class of 

 Mammalia. The surface of the crown presents three series of 

 enamel-islands, in the direction of the long axis of the grinding 

 surface ; the eight or nine islands of the middle row are elliptic 

 and simple ; those of the other rows are equal in number, but are 



