286 UNGOLATA 
specimens in the London Zoological Gardens has, however, afforded 
opportunities for careful anatomical observation.t 
C.—Two well-marked species of African Swine have been with 
more reason separated under the name of Potamecherus. The denti- 
tion differs from that of the true Svs, Inasmuch as the anterior 
premolars have a tendeney 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 
Fi. 107.—The Red River-Heg (Sus poreus). From Selater, Guide to Animals 
in Zoological Society's Gardens, 1833, 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 8. africanus, the South African River-Hoe, 
or Bosch-Vark, of a gray colour, and the other S. percus, 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. sa/ranius, present the striped 
character of the true Sus, a strong indication of close attinities. 
whereas in all the following forms this is absent. 
The genus Svs, in the above exténded 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, Proce. Zool. Sov. Lon’?, 1S82, p. £13. 
