48 Dr. J. E. Gray on the Skulh of Potainocluvrus. 



»• 



The ziigomatic arch swollen out, broad in the middle, and with a pro- 

 duced std>antjidar lower edije ; the impreasion on the side of the 

 forehead rather ywrrow, obliqueli/ truncated, produced above so 

 as to have an ohliq\ie edge, extending forward in front of the 

 orbit ; lotver jaw with a perforation for the passage of the vessel 

 under the sjMce between the first and second lower grinders ; the 

 front of the upper part of the nose narrotv,fUittish, rounded on 

 tJu sides. 



Potamochoerus Edwardaii. 



The lobe over the sheath of the ujiper canines elongate, 

 adpressed, and reaching the callosity of the lateral ridge on 

 the side of the nose. 



The lobe over the base of the sheath of the canines in tlie 

 males is elongate and adpressed to the sides of the nose, as in 

 P. africanus, and not short and diverging outwards as in 

 P. porcus. The skull lias a much slenderer nose, is much 

 lower behind, and has a narrower occi])ital end than in either 

 of the continental species, in both of which it is high and 

 broad behind and has a broad square nose. 



The skulls of the female river-hogs [Potamochoerus) only 

 hav^e a sharj) ridge across the base of the sheath of the canines ; 

 and the sides of the nose are smooth, and not callous and warty 

 in the middle part as in the males ; and the impressions on the 

 sides of the forehead just before the eyes are not so deep and 

 well marked as in the skulls of the males ; and the lobe of the 

 maxillary bone forming the front portion of the maxillary 

 arch is broader than in the males. 



The lobe over the base of the canines of the males of 

 P. porcus is compressed, callous, and rugose at the ends. 

 It seems to vary in shape : in two skulls in the Museum 

 from the Cameroons and Gaboon it is moderately broad, 

 ■with a rounded outer edge and a convex rounded outer sur- 

 face ; and in one from West Africa ( believed to be from the 

 Niger) it is flattened, broader, and with a much flatter 

 surface. The lobes over the base of the canines of the 

 males of P. africanus are longer and broader ; one has 

 a distinct keel on the hinder part of the outer side ; and 

 the other has but very sliglit indications of such a keel and 

 is rounded. 



