1865.] PRESBYTES AND COLOBUS. 743 
this respect. The supraciliary ridges are higher and more marked 
in P. albigena; in the Semnopitheci the frontal bone is depressed 
immediately behind the ridges, which are thinner, projecting slightly 
forwards. 
The nasal bones in the genus Semnopithecus are short, nearly 
straight, and flat ; in P. albigena, asin the genus Cercocebus, they are 
more elongated ; in the latter they are wider inferiorly, in the former 
relatively somewhat wider superiorly, so that Semnopithecus has the 
widest root of nose. The nasal cavity in all the Semnopitheci 
extends rather higher than the lower margin of the orbit, in Cerco- 
cebus ethiops and C. fuliginosus it does not reach the orbit by as 
much as the other genus goes above, and in P. albigena, while agree- 
ing with these last species, it is even slightly lower. The compa- 
rative breadth of the face opposite the two maxillary bones is rela- 
tively broadest and more entirely truncated in the Semnopitheci, 
while P. albigena again corresponds to the Cercocebi in the progna- 
thous and narrower appearance of these bones. Some species of the 
genus Semnopithecus present a curious character in the remarkable 
truncation of the occipital region, S. johnii and S. maurus having it 
nearly perpendicular ; this gives the cranium, when resting on the 
mandible, a curious forward expression. P. albigena, like Cerco- 
cebus, has this part more shelving; Semnopithecus melalophus and 
S. obscurus make an approach to this in their contour. 
The bony palate in Cercocebus fuliginosus and C. ethiops is longer 
and not relatively so broad as in Semnopithecus; the length of the 
premaxillary produces this. P. albigena has this character well 
marked. 
The depth of the lower jaw in Semnopithecus is greatest, the same 
only being found in the genus Colodus. In the P. albigena and Cer- 
cocebus the angle of the mandible is less perpendicular and more 
rounded than in S. melalophus and S. obscurus; in many of the 
other species of Semnopithecus, e.g. in S. johnit and S. entellus, it 
is even inclined backwards. 
The teeth in the several genera spoken of are alike in number. 
The two inner and upper incisors are very much the largest, and 
project considerably in the two species of Cercocebus examined ; they 
are precisely similar in the specimen of P. albigena. The Semno- 
pttheci have all the incisors small and of nearly equal size. 
In the true species of Semnopithecus, as likewise in Colobus, the 
canines, as compared with the other teeth, are considerably larger ; 
in Cercocebus and in P, albigena they are not so massive. In the 
last-named genus and species the cusps of the molars are more 
rounded, while they are acuminate from before backwards in Sem- 
nopithecus and Colobus. The upper penultimate molar in Cercoce- 
éus and the species under consideration is largest ; in all the Semno- 
pitheci the molars are more nearly alike in size. P. albigena and 
the Cercocebi can hardly be said to possess a fifth cusp in the upper 
posterior molar; in their lower jaw it is very rudimentary. The 
lower incisors in P. albigena are more horizontally set, and the ca- 
nines less curved, than im any of the Semnopitheci; in this respect, 
