546 UNGULATES. 



the canine of a horse. Castration arrests the development of the 

 tusks in the male. 



The teeth of the molar series progressively increase in size 

 from the first to the last : the first premolar (PI. 140, fig. 1, p 1) 

 has a simple compressed conical crown, thickest behind, and has 

 two fangs : it is further removed from the second in the Sus 

 larvatus than in Sus scrofa. The second premolar (ib. p 2) has a 

 broader crown, with a hind-lobe, having a depression on its inner 

 surface ; and each fang begins to be subdivided. The third premolar 

 (ib. p 3) has a similar but broader crown implanted by four fangs. 

 The fourth premolar (ib. p 4) has two principal tubercles and 

 some irregular vertical pits on the inner half of the crown. In 

 the masked Boar the third upper premolar is larger, thicker, and 

 more pointed than in the common Boar. The first true molar, when 

 the permanent dentition is completed, exhibits the effects of its early 

 development in a more marked degree than in most other Mammalia, 

 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 (PI. 141, fig. 3, m 1) : 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 (ib. m 2) with more complex 

 shallow subdivisions and a larger tuberculate posterior ridge. The 

 greater extent of the last molar (ib. m 3) is chiefly produced by 

 the development of the back ridge into a cluster of tubercles : 

 the four primary cones being distinguishable on the anterior main 

 body of the tooth. The hind lobe is more simple and smaller in 

 the masked than in the common Boar. There is generally a small 

 tubercle at the outer and inner interspace between the two 

 principal lobes of the true molars. The number of fangs increases 

 with the increasing size of the crown. 



The crowns of the lower molars are very similar to those 

 above, but are rather narrower, and the outer and inner basal 

 tubercles are much smaller or are wanting. The transverse 



