MONKEYS. 139 
anterior members, with long and flexible fingers and 
opposable thumbs, which constitute the primary charac- 
ters of the order, the Monkey tribe in general is distin- 
guished by the following peculiarities. Their incisor 
teeth are invariably four in each jaw, and their molars, 
like those of man, are flat and surmounted by blunted 
tubercles. The latter are five in number on each side of 
either jaw in all the Monkeys of the Old Continent, and 
in one very distinct tribe belonging to the New; but 
most of the American species are furnished with a sixth. 
Their canines vary considerably in size, from a trifling 
projection beyond the remaining teeth to a long and 
powerful tusk, almost equalling those of the most formi- 
dable Carnivora; and from this structure it necessarily 
follows that a vacant space is left between the incisors 
and the canines of the upper jaw, and between the 
canines and the molars of the lower, for the reception 
and lodgment of those organs when the mouth is closed. 
The nails of all their fingers, as well as those of the 
thumbs, are invariably flat and expanded. 
In almost every other point they are subject to infinite 
variations of form and structure. The shape of the head, 
which, in one or two species, offers a close approximation 
to the human form, passes through numerous interme- 
diate gradations, until it reaches a point at which it can 
only be compared with that of the hound. The body, 
which is in general slight and well made, is in some few 
instances remarkably short and thick-set, and in others 
drawn out to a surprising degree of tenuity. Their limbs 
vary greatly in their proportions; but in most of them 
the anterior are longer than the posterior: in all they 
are admirably adapted to the purposes to which they 
