5G2 



UNGULATES. 



premolars in this jaw, the first with a compressed pointed crown 

 and a small posterior talon, like that above ; the second and third 

 increasing in breadth, but narrower and more simple than those 

 above. The true molars below are also narrower than the upper 

 ones, but are quadricuspid with accessory tubercles, and a largely- 

 developed hinder talon in the last molar. Nothing as yet is known 

 of the incisors of the Chceropotamus ; the rest of the dentition 

 closely resembles that of the Peccari, but the premolars are more 

 simple and the canines by their size, shape, and direction, and 

 the lower jaw by the backward prolongation of its angle, alike 

 manifest a marked approximation to the Ferine type. The occasional 

 carnivorous propensities of the common Hog are well known, and 

 they correspond with the minor degree of resemblance, which this 

 existing Pachyderm presents to the same type. The extinct 

 Chcsropotamus, still better adapted by its dentition for predacious 

 habits, presents an interesting example of one of those links, 

 completing the chain of affinities, which the revolutions of the 

 earth's surface have interrupted, as it were, and for a time 

 concealed from our view. 



203. Hippohyus. — In this extinct genus of quadrupeds from the 

 Himalayan tertiary deposits, the dental formula shows incisors 

 |r|, and corresponds with that of the Chceropotamus in the number 

 of canines, premolars, and molars ; but the true molars have a more 

 complex crown, approaching nearer to those of the typical Suidce in 

 the depth and number of the secondary enamel-folds. Each upper true 

 molar (PI. 140, fig. 7) has its crown cleft by the common or primary 

 crucial valleys, the transverse one passing somewhat obliquely from 

 within forwards and outwards. Each of the four principal lobes is 

 subdivided, not by a vertical central depression, but by a fold 

 penetrating its anterior and posterior margins : the enamel at first 

 shows additional minor plications ; but is worn down progressively to 

 the simpler pattern above described; the outer lobes are convex 

 externally. The first premolar is very small and simple, separated 

 by an interval of its own breadth from the second : both this and 

 the third have transversely compressed crowns, the fourth has a 

 sub- trihedral crown. The Hippohyus equalled in size the Chcoropo- 



