HIPPAEION AND ANCHITHEEIUM. 359 



molars there is a cok;mn sucli as exists in the Stags. Of 

 this a rudiment exists, as a fold, in the corresponding teeth 

 of the existing Horse. 



In the geuus Anchitherium, 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 pro- 

 portion than in the Horse, and the jaws are more slender. 

 The hindermost molar tooth is situated farther back under 

 the orbit, and the orbit itseK is not completely encircled by 

 bone, as it is in the Horses and Hipparions. 



The shaft of the ulna is stouter than in Hippm-ion, 

 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, how- 

 ever, the middle of the shaft seems to have been incom- 

 pletely ossified. Not only are there three toes in each foot, 

 as in Hipparion, but the inner and the outer toes ai-e so 

 large that they must have rested upon the ground. Thus, 

 so far as the limbs are concerned, the Anchithermm is just 

 such a step beyond the Sipparion, 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, and 

 their crowns lack the peculiar pit which characterizes those 

 of Equus and Hipparion. The first grinder is proportion- 

 ately much larger, especially in the iipper jaw, and like the 

 other six has a short crown and no thick coat of cement. 

 The pattern of their crowns is wonderfully simplified. 

 The fore and hind ridges run with but a slight obliquity 

 across the crown, and the pillars are little more than en- 

 largements of the ridges, while in the lower jaw these 

 pillars have almost disappeared. But the foremost of the 

 six principal grinders is still somewhat larger than the 

 rest, and the posterior lobe of the last lower molar is small, 

 as in the other Equidce. 



