HIPPAKION AND ANCHITHERIUM. 307 



and their crowns lack tbe peculiar pit which characterizea 

 those of JEquus and Bipparlon. The first grinder is propor- 

 tionately much larger, especially in the upper 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 enlargements of the 

 ridges, while in the lower jaw these pillars have almost disap- 

 peared. 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 Equidae. 



In all those respects in which Anchitherium daparts from 

 the modern Equine type, it approaches that of the extinct 

 PaloBOtheria / and this is so much the case that Cuvier con- 

 sidered the remains of the Anohitherium with which he was 

 acquainted to be those of a species of Palceotherium. 



b. In the Rhinocerotidce the second, third, and fourth toes 

 are nearly equally developed in both the fore- and the hind- 

 feet. 



The dental formula is i. ^ or i. —^ c. ^^p.m. i^ ni. |,|. 



But the teeth differ from those of the Horse in many other 

 respects besides the number of the incisors and the absence of 

 canines. Thus, the upper incisors diBFer greatly in form from 

 those which are situated in the lower jaw ; and, in some spe- 

 cies, incisors are absent. Their crowns are not folded as in 

 the Horse. The peculiarities of the grinding teeth will be 

 mentioned below. 



The skin is very thick and may be converted into a jointed 

 armor ; the hair is scanty. The upper lip is much produced 

 and is very flexible. In some species one, or sometimes two, 

 horns are attached in the middle line to the nasal or frontal 

 bones. But these horns are formed, as it were, by agglomer- 

 ation of a great number of hair-like shafts. 



The distal phalanges of the tridactyle feet of the Rhinoce- 

 ros are invested by small hoofs ; but these do not entirely 

 support the weight of the body, which rests, in great measure, 

 upon a large callous pad developed from the under face of the 

 metacarpal and metatarsal regions ; these are much shorter 

 than in the Horse. 



The dorso-lumbar vertebra; are twenty-two or twenty-three, 

 of which twenty are dorsal. There are four sacral and twen- 

 ty-two caudal. The cervical vertebras, as in the Horse, are 

 strongly opisthocoelous, and the transverse processes of the 



