PKRI8SODACTYLA 



The existing representatives of the suborder naturally 

 arrange themselves in the three following families : 



A. No cranial appendages ; a full series of front teeth. 



a. A single functional digit on each foot ; * cheek- 



teeth tall-crowned (hypsodont) and com- 

 plex. Europe,t Asia (exclusive of almost 

 the whole of the Oriental region), and 

 Africa Equid-as. 



b. Four front and three hind toes ; cheek-teeth 



low -crowned (brachyodont) and simple. 



Malaya and Central and South America... Tapir idae. 



B. Cranial appendages, in the form of one or two 



solid conical horns,:}: placed in the median line ; 

 front teeth incomplete or wanting ; feet three- 

 toed. India, Malaya, and Ethiopian Africa Ftkinocerotidx. 



FAMILY I. EQUID^E. 



Long-headed, long-limbed, and slenderly built hypsodont 

 perissodactyles, with not more than three toes to each foot, 

 of which the middle one is stouter than the laterals, and in 

 the existing species is the only one present, the lateral pair 

 being represented solely by the splint-bones (fig. 1, A, II, IV) ; 

 hoofs compact and box-like ; skull long and low, with 

 elongated nasals, and the orbits encircled by bone (fig. 2) ; 

 central valleys of ,the tall-crowned cheek-teeth completely 

 filled with cement, and their enamel thrown into complex 

 folds (fig. 3) ; upper premolars as complex as, and rather 

 larger than the molars ; summits of the incisors with the 

 enamel infolded in a pocket-like manner; ulna and fibula 

 incomplete at their lower ends, and the mesocuneiform bone 

 of the tarsus welded with the entocuneiform. In females 

 the canines are small or wanting. 



All the existing forms may be included in the single 

 genus Equus, which has a range over North-eastern Europe 

 (now extinct there), Asia Minor and Syria, Persia, Balu- 

 chistan, and the deserts of North-western and Central India, 

 Central Asia, and Africa south of the Sahara. During the 



* Three toes in many extinct forms. 



f Now exterminated in a wild condition ; in the Tertiary period 

 the range included America. 



% Absent in certain extinct forms, and said to be absent in the 

 female of the recent Rhinoceros sondaiciis. 



B 2 



