1 84 EASTERN ARCTOGvEA. [CHAP. 



morphous section of the order, but among the Hystricomorphous 

 rodents we have the typical porcupines (Hystricince), in which the 

 tail is never prehensile, practically confined to Eastern Arctogsea, 

 where they range over south-eastern Europe, and the Ethiopian 

 and Oriental regions. The Javan species of the typical genus 

 (Hystrix javanicd] is, however, found in the island of Timor, 

 in the Austro-Malayan region, although it is doubtless of late 

 introduction there, and may not improbably have been transported 

 by human agency. In a fossil state porcupines of this sub-family 

 are common in the European Tertiary as far down as the lower 

 Oligocene. 



Turning to the ungulates, we have in the artiodactyle section 

 two closely allied families, which if we except certain pigs from the 

 Austro-Malayan region and Papua, which may have been originally 

 introduced by man are restricted to the area under considera- 

 tion. Both these families, moreover, have representatives, either 

 living or extinct, in all the regions of Eastern Arctogsea, inclusive 

 even of Madagascar, so that they may be reckoned among its most 

 characteristic mammals. The Hippopotamidtz now restricted to 

 the Ethiopian region, where they are represented by the widely- 

 spread common Hippopotamus amphibius, and the much smaller 

 terrestrial H. liberiensis of the West Coast ranged during the 

 Plistocene and upper Pliocene epochs over the greater part of 

 Europe as far north as England ; one species from these deposits 

 being apparently indistinguishable from the common African form. 

 Extinct species are met with in the Plistocene of Algeria, the 

 Plistocene and Pliocene of India, the Pliocene of Burma, and the 

 superficial deposits of Madagascar; some of these differing from 

 the common hippopotamus by the presence of three, in place of 

 two, pairs of incisor teeth in each jaw. Whatever may have been 

 the case with the swine, it is evident that the hippopotami were 

 never able to exist sufficiently far north to cross by way of Bering 

 Strait into the New World. In the pigs (Suidez) which among 

 other features differ from the Hippopotamidce by the nostrils being 

 perforated in a fleshy disc at the extremity of the muzzle, and like- 

 wise by the structure of the teeth the typical group of the genus 

 Sus ranges over most of the Eastern Holarctic and the whole 

 of the Oriental region, being replaced in the Ethiopian and 



