364 BR. c. I. roRSYTH MAJOR ON THE [Mar. 16, 



account of its being the only Ungulate of the recent Malagasy- 

 fauna and closely related to the species of an African genus ; 

 whilst all the other Mammals, with the exception of the Chiroptera, 

 a Crocidura, and the Viverricula, belong to distinct genera. For 

 this reason it has been supposed by Blanford that the genus 

 PotaniocJuerus did not exist in Africa when Madagascar was con- 

 nected with that continent, but found its way there at a later time 

 (at the end of the Pliocene or later Pleistocene), when the con- 

 nection with Africa was severed, so as to prevent most of the pre- 

 sent African Mammalia from crossing over ; whilst Fotamochoerus, 

 being a good swimmer, might have been able to cross the Strait. 

 This hypothesis reposes, of course, on two assumptions : first, 

 that the Strait of Mozambique Mas very much narrower in later 

 Pliocene times than at present ; and secondly, on its being taken for 

 granted that the Malagasy Potamochosrus is diilerent from all its 

 African congeners. Por it is obvious that if the Malagasy Wild 

 Hog is specifically identical with one of the continental species, it 

 must have arrived in the island at a very recent date ; and in that 

 case, the most likely supposition would be that for some reason or 

 other it had been carried over by man, as must be supposed to have 

 been the case with regard to Viverricula malaceensis. 



The question as to the specific distinctness is not in the least 

 settled at present. There has been in the Natural History Museum, 

 for some months, a mounted specimen of a Potamochcertis from 

 Nyasaland, which in colour and general outer appearance so 

 closely resembles the Malagasy form that very few zoologists 

 would venture to separate them on account of some slight dif- 

 ferences in the respective skins. On the other hand, most of the 

 cranial characters mentioned as distinctive between the Malagasy 

 form and the P. choeropotamus ' are of such little value, being 

 very variable, that no importance can be attached to them. Such 

 are : the position of the mental foramina in the lower jaw, the 

 more or less irregularity in the lo\\'er contour of the zygomatic 

 arch, and the conformation cf the lateral depression in the 

 region of the lachrymal and the upper part of the maxiDary. 



Up to the present time, besides the skin of a very yoimg specimen, 

 only one skull of the Malagasy form, that of an adult male, existed 

 in the Natural History Museum. I have brought back from the 

 Upper Forest Eegion of the island the remains of eight specimens, 

 viz. six skins with their skulls complete, besides a complete skeleton 

 and a separate skull, making in all eight skulls of different ages and 

 both sexes. Two of the skulls, a male (see figs. 1 and 2, p. 365) 

 and a female (PL XXV. fig. 2 and PI. XXVI. fig. 2), are now ex- 

 hibited. As a result of my comparisons I have to state that there 

 are very constant cranial characters whicb enable us to distinguish 

 the Madagascar form from the P. cheer opotmnus, with v^hich, on the 

 whole, it has more affinities than with the West- African P. porcus, 



' J. E. Gray. " On tlie Madagascar Eiver-h.ig (Pofamochoerus) and on tlie 

 Skulls of the three Species of the Genu- " (Ann. & Mag. K. H. xv. 1875, p. 45). 



