Zoological Society. 487 
elongation of the palate; by the small proportional size of the infra- 
orbital foramen ; by the obliquity of the occipital plane, and by the 
large size of the canine teeth; by the elongation of the lower jaws, 
in consequence of the length of the muzzle and palate; by the in- 
creased depth of the symphysis, and by the small size of the foramen 
which gives exit to the blood-vessel nourishing the teeth and the 
accompanying aerve. 
This skull agrees with that of the Chimpanzee in its smallness 
proportionally to the body, in its generally elongated form, in its 
anterior contraction, in the marks of the attachments of the temporal 
muscles, in the large supraorbital ridges, in the obliquity of the plane 
of the foramen magnum, and in the slight arch of the nasal bones. 
It differs from that of the Chimpanzee in the supraorbital ridges 
not uniting, in the obliteration of the sutures, in the smaller size of 
the infraorbital foramen and of the foramen of the dental blood-vessel. 
The lower jaw is proportionally shallower. The cranium of the 
young Chimpanzee is far broader, more arched and less anteriorly 
compressed, and therefore far more anthropoid. ‘These characters 
however degenerate with age. 
It differs yet more from the form of skull exhibited by the adult 
Orang Utan, where the strongly developed cranial ridges and widely 
expanded zygomatic arches give the skull a carnivorous aspect. 
These peculiarities we have seen to be absent in the Gibbon. The 
flatness of the bones of the nose of this Ape is an additional distinc- 
tion. On the other hand, it agrees with the Orang in the oblitera- 
tion of the cranial sutures of the adult. 
In the large development of the supraciliary ridges this skull re- 
minds us of the Baboons, which present however a more degraded 
form, and may be distinguished by the greater narrowness of the 
cranium, by the less circular form of the orbits, by the greater pro- 
longation of the muzzle and the greater spree between the zygomatic 
arch and the skull. 
The dentition of the Gibbon claims no especial notice; the in- 
cisors and molars are moderate in size, whilst the canines are large, 
their roots apparently reaching nearly to the internal corner of the 
orbits. 
Section I1.—Or tur Trunx. 
The vertebral formula of the Agile Gibbon is—cervical, 7 ; dorsal, 
13; lumbar, 5; sacral, 4; coccygeal, 4. The comparison of these 
numbers with those of some of its congeners and near allies will be 
exhibited by the following table :— 
Name of Animal. Cervical. | Dorsal. | Lumbar, | Sacral. | Coccygeal. || Total. 
EF oicusieews cs oe 7 12 5 5 4 33 
Chimpanzee ...... 7 13 4 5 4 33 
Orang Utan ...... 7 12 4 5 3 31 
Hylobates concolor. 7 14 5 5 5 36 
‘|Hylobates lar ...... 7 12 6 3 3 31 
Hylobates agilis ... 7 13 5 4 4 33 
Of the cervical vertebree I need only remark, that the transverse 
