PIGS, PECCARIES, AND HIPPOPOTAMI. 421 



crescentic columns of great height, and separated by deep pocket-like pits, while 

 on the same page there is also represented the corresponding tooth of an extinct 

 Ungulate, in which the same columns, although still crescent-like, are very much 

 lower, and are separated by quite shallow valleys, of which the base is visible from 

 the surface. Now from such a tooth there is but a step to the teeth represented in 

 the woodcuts on the present page, marked 1 and 2. It will be observed, however, 

 that the front inner column of the Ruminant molar is here divided into two 

 moieties {pi. p), so that the tooth becomes five-columned. The molar represented 

 in Fig. 1 is that of the anoplothere, a two or three-toed Ungulate from the 

 upper Eocene rocks of Europe, furnished with the full number of forty-four teeth. 

 The one marked 2 belongs to the so-called Hyopotamus, which also occurs in the 

 upper Eocene rocks. It will be noticed that the columns of the latter, although 

 very low, still have an imperfect crescentic shape ; but in the allied anthracothere 



p hy 

 Fig. 1 



Fig. 



LEFT UPPER MOLAR TEETH OF EXTINCT PIG-LIKE ANIMALS. 



1, Anoplothere (after Gaudry) ; 2, Hyopotamus ; 3, Hyothere. (The specimen represented in the 

 second figure is imperfect on the anterior side). 



of the same horizon this structure is far less apparent, and the columns assume 

 the form of flattened cones. From such a tooth the transition is easy to the type 

 of the pair marked 3 in our illustration, which belonged to an extinct pig known 

 as the hyothere. In the latter figure it will be seen that each tooth carries four 

 low, conical, hillock-like columns, or tubercles, the column marked pi in the molar 

 of the anoplothere having almost completely disappeared. From the hillock-like 

 form of the columns the type of tooth found in the pigs is known as the bunodont 

 (Gr. bounos, a hillock) form, in contradistinction to the selenodont (Gr. selene, the 

 crescent-moon) form distinctive of all the ruminating Ungulates. This essential 

 distinction in the structure of their molar teeth is the most readily recognised 

 characteristic by which the pig-like Ungulates are distinguished from all those 

 treated in the preceding chapters ; but from the transition between one type and 

 the other indicated by extinct forms, it is perfectly clear that the true Ruminants, 

 the chevrotains, and the camels, are all severally descended from bunodont 

 ancestors. 

 Characters of The pigs and their allies are further distinguished from the true 



Pi & s - Ruminants and camels, by the metacarpal and metatarsal bones of the 



two main digits of the feet remaining distinct instead of being fused into a cannon- 



