iocs THE UNGULATES, OR HOOFED MAMMALS 



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

 late, 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 sur- 

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

 cuts on the present page, marked i and 2. It will be observed, however, that the 

 front inner column of the Ruminant molar is here divided into two moieties (/>/. />), 

 so that the tooth becomes five columned. The molar represented in figure i is that 

 of the anoplothere, a two or a three-toed Ungulate from the upper Eocene rocks of 

 Europe, furnished with the full number of forty-four teeth. The one marked 2 be- 

 longs 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 im- 

 perfect crescentic shape; but in the allied anthracothere 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 



I,EFT UPPER MOI,AR TEETH OF EXTINCT PIG-I,IKE ANIMALS. 



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

 second figure is imperfect on the anterior side.) 



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 recognized characteristic by which the pig-like Ungu- 

 lates 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. 



Characteristics ^ he P* gs and t ^ ie ^ r a ^ es are further distinguished from the true 



of Pigs 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 canon bone, while in the fore-limb at least the lateral toes are likewise fur- 



