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 
Fig. 2 
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- 
