590 CHORDATA. 
to the rest of the Przmates they have only two molars. Their dental 
formula is 3433. All the digits except the hallux are clawed and the 
pollex is present but not opposable to the other digits. They have a 
long, bushy tail and are strictly arboreal. 
Family 2,—Cebidz.—The American Monkeys. They are confined 
to Neogcea, are strictly arboreal and often have prehensile taik. 
Their dental formula is 343, hence they differ from the Hapalide in 
having an additional molar. They also have a pollex to a large 
extent opposable. They include the Spider-monkeys and Capuchins. 
Fig. 396.—FRONT VIEW OF SKULL OF A GORILLA. 
Note forward position of the complete orbits, the (vertical) sagittal crest, 
the two incisors (2) and the rather longer canines. 
2.2. 
Family 3.—Cercopithecidz.—All this family of Monkeys is found 
in the Old World, mainly in the Oriental and Ethiopian regions. 
The tail is not prehensile but is often of great length. There are 
usually brightly coloured ischial callosities. The pollex, if present at 
all, is always opposable, and the front-limbs are always markedly 
shorter than the hind-limbs. The dentition is 212%. All the best 
known monkeys belong to this family, including the baboons (Cyzo- 
cephalus) of Africa, which are not arboreal but frequent rocky regions 
in communities, and the familiar Macaques (AZacacus) of Asia. 
Family 4.—Simiidz.—The family of Anthropoid Apes. They 
are all found in the Old World and comprise the Gorilla: and Chim- 
-panzee of equatorial Africa, the Orang of Borneo and the Gibbons of 
the Oriental region. They mostly have no tail; there are never ischial 
callosities. The pollex is always opposable and the front-limbs always 
exceed the hind-limbs in length. The dentition is 3433. 
