306 THE ANATOMY OF ^/ERTEBRATED ANIMALS. 



soraewliat like that wliicli lodges the "larmier" of a stag 

 (traces of which are observable in some of the older species 

 of JEquus) ; otherwise the cranium is altogether like that of 

 a Horse. Again, the shaft of the ulna is very slender, but it 

 is larger than in the Horse, and is distinctly traceable through- 

 out its M^hole length although firmly anchylosed with the 

 radius. The distal end of the fibula is so completely anchy- 

 losed with the tibia, that, as in the Horse, it is difficult to 

 discern any trace of the primitive separation of the bones. 

 But, as has been already mentioned, each limb possesses three 

 complete toes — one strong, median, and provided with a large 

 hoof, while the two lateral toes are so small that they do not 

 extend beyond the fetlock-joint. In the fore-limb, rudiments 

 of the first and fifth toes have been found. 



The teeth are exceedingly like those of the Horse, but the 

 crowns of the molars are shorter; and, in the upper jaw, that 

 which, in the true Horses, is a large fold of the inner face of 

 the tooth becomes a detached pillar. The smaller plications 

 of the enamel are also more numerous, close-set, and compli- 

 cated. On the outer face of the lower milk-molars there is a 

 column such as exists in the Stags. Of this a rudiment exists, 

 as a fold, in the corresponding teeth of the existing Horse. 



In the genus AnGhitherium^ all the known remains of 

 which are of older miocene (and, perhaps, newer eocene) age, 

 the skeleton in general is still extraordinarily like that of a 

 Horse. The skull, however, is smaller in proportion than in 

 the Horse, and the jaws are more slender. The hindermost 

 molar tooth is situated farther back under the orbit, and the 

 orbit itself is not completely encircled by bone, as it is in the 

 Horses and Hipparions. 



The shaft of the ulna is stouter than in IIipiJari07i^ and is 

 less closely united with the radius. The fibula appears, at any 

 rate in some cases, to have been a complete though slender 

 bone, the distal end of which is still closely united with the 

 tibia, though much more distinct than in the Hipparions and 

 the Horses. In some specimens, however, the middle of the 

 shaft seems to have been incompletely ossified. Not only are 

 there three toes in each foot, as in Illppafrion^ but the inner 

 and the outer toes are so large that they must have rested 

 upon the ground. Thus, so far as the limbs are concerned, the 

 Anchitheriwn is just such a step beyond the Uippcf/non^ as 

 the Hipparion is beyond the Horse, in the direction of a less 

 specialized quadruped. The teeth are still more divergent 

 from the Equine type. The incisors are smaller in proportion, 



