48 Dr. J. E. Gray on the Skulls of Potamochcerus. 
** The zygomatic arch swollen out, broad in the middle, and with a pro- 
duced subangular lower edge ; the impression on the side of the 
forehead rather narrow, obliquely truncated, produced above so 
as to have an oblique edge, extending forward in front of the 
orbit ; lower jaw with a perforation for the passage of the vessel 
under the space between the first and second lower grinders ; the 
Front of the upper part of the nose narrow, flattish, rounded on 
the sides. 
Potamocherus Edwardsiv. 
The lobe over the sheath of the upper 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 the 
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 has a much slenderer nose, is much 
lower behind, and has a narrower occipital 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 (Potamocherus) only 
have a sharp 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 slight indications of such a keel and 
is rounded. 
