286 



UNGULATA 



specimens in the London Zoological Gardens has, however, afforded 

 opportunities for careful anatomical observation. 1 



C. Two well-marked species of African Swine have been with 

 more reason separated under the name of Potamochcerus. The denti- 

 tion differs from that of the true Sus, inasmuch as the anterior 

 premolars have a tendency to disappear; sometimes in adult 

 specimens the first upper premolar is retained, but it is usually 

 absent, as well as the first and often the second lower premolars. 

 The molar teeth are also less complex ; the last especially having a 



FIG. 107. The Red River-Hog (Sus porous). From Sclater, Guide to Animals 

 in Zoological Society's Gardens, 1883, p. 183. 



much less developed talon. There are likewise characteristic cranial 

 differences. The two species are very distinct in outward appearance 

 and coloration. One is S. africanus, the South African River-Hog, 

 or Bosch-Vark, of a gray colour, and the other S. porcus, the West 

 African Red River-Hog (Fig. 107), remarkable for its vivid colouring 

 and long pencilled ears. It should be noted that the young of both 

 these species, as well as of the pigmy S. salvanius, present the striped 

 character of the true Sus, a strong indication of close affinities, 

 whereas in all the following forms this is absent. 



The genus Sus, in the above extended sense, is well represented 

 in the Tertiaries of the Old World from the period of the Lower 

 Pliocene upwards. In the Pliocene and Pleistocene of India 

 1 See Garson, Proc. ZooL Soc. Lmid. 1883, p. 413. 



