VII.] UNGULATES. 247 



antelopes; while in the elands (Orias) 1 the horns are present in 

 both sexes and form a close spiral. 



Turning to the perissodactyle section of the order, we find 

 Ethiopian Africa the home of several species differing markedly 

 from any now living in other parts of the world, although, accord- 

 ing to the system here adopted, these do not constitute generic 

 groups by themselves. There are two, or possibly three species of 

 Rhinoceros, both of which are two-horned, and differ from those of 

 the Oriental region in the absence of canine and incisor teeth. Of 

 these the common African rhinoceros (R. bicornis) is closely allied to 

 an extinct species from the Pikermi beds of Attica; while Burchell's 

 rhinoceros (R. simus), which is now nearly exterminated, has its 

 nearest allies in the extinct R. platyrhinus of the Siwalik Hills, and 

 the woolly rhinoceros (R. antiquitatis) of the Plistocene of Europe 

 and northern Asia. In addition to being the habitat of the parent 

 form of the domestic ass, which is confined to Somaliland and the 

 adjacent regions, Ethiopian Africa is also characterised by contain- 

 ing all the striped horses, or zebras, separated by some authorities 

 as a distinct genus, under the name of Hippotigris. The best 

 known representatives of this group are the true or mountain 

 zebra (Equus zebra], Burchell's zebra (E. burcheili\ Grevy's zebra 

 (E. grevyi] of the Galla country, and the quagga (E. quagga). The 

 latter, although formerly abundant in the southern extremity of the 

 continent, is now fast verging on extinction, and serves to connect 

 the more typical members of the group with the true asses. In 

 spite of the difference in their coloration, the zebras are indeed 

 indistinguishable in their osteology and dentition from the latter, 

 and it is quite possible that they are represented in a fossil state in 

 the later Tertiaries of Europe, while they are not improbably the 

 direct descendants of the ancestral genus Hipparion. The absence 

 of tapirs from the Ethiopian region is as remarkable as the want 

 of deer ; but it is noteworthy that the former are unknown among 

 both the Pikermi and Siwalik faunas. 



Although the African elephant (Elephas africanus) is markedly 

 distinct from the Oriental species, yet the two are so closely con- 

 nected by intermediate extinct forms that it is impossible to regard 



1 The name is usually spelt Oreas, but as it is derived from <5/>etds, the 

 proper orthography is Orias. 



