THE UNGULATA, 47 



potamochosrus or river-hog, closely allied to an African species. 

 It is described by a French writer as an ugly animal, with 

 high withers, low back, and little hair. It has an enormous 

 tubercle, supported by a bony prominence in the jaw, which 

 renders the face of the animal extremely disagreeable. The 

 specimen in the British Museum hardly bears out this not 

 very flattering portrait; but I fancy it is a young one, in 

 which the adult ugliness above described has not been de- 

 veloped. I have never seen this hog in Madagascar, but have 

 frequently met with its tracks in the forest, where it digs up 

 the ground in search of roots, and often does much damage 

 to plantations situated near the woods. The presence in 

 Madagascar of this single peculiar species of river-hog, with 

 so near a relative in Africa, may, in the opinion of Mr. 

 Wallace, " be perhaps explained by the unusual swimming 

 powers of swine, and the semi-aquatic habits of this genus 

 leading to an immigration at a later period than in the case 

 of the other mammalia." * 



But although the larger pachydermata are now absent from 

 Madagascar, it is an interesting fact that they have not all of 

 them been so in former times ; for M. Grandidier has dis- 

 covered the bones of a small species of hippopotamus (IT. 

 lemerlii) in the south-west provinces in a sub-fossil state, 

 indicating that this quadruped was an inhabitant of the island 

 at a not very remote period. A large proportion of the mari- 

 time plains of Madagascar has extensive reaches of river and 

 lagoon, which would seem to be just the sort of country best 

 suited to the habits of the hippopotamus ; so that it is diffi- 

 cult to account for the fact of its having become extinct. 

 But this is only one of those numerous yet unsolved problems 

 with which the subject of the geographical distribution of 

 animals abounds. 



Rodentia. — The only remaining order of mammalia, found 

 in Madagascar is that of the Bodentia, represented by three 

 genera, each with a single species of Muridce, about which 

 there is nothing of special interest to remark. Although 

 poor in genera and species, however, this family is very rich 

 indeed in individuals ; for the whole inhabited parts of the 

 * "Wallace, op. cit., vol. i. p. 273. 



