_Ateles_, Geoffr., Ann. Mus., vii., p. 262 (1806).
This is the fourth remaining genus of the _Cebinæ_, the last Sub-family of
the _Cebidæ_. With the description of the Spider-Monkeys, therefore, we
shall have passed in review all the species of the New World Platyrrhine
section of the _Anthropoidea_. The species of this group derive their
trivial name from their long and slender limbs; the name applied to them,
however, in their native forests by the Indians of Brazil is "Coaita." They
are characterised by their light and slender body, which is narrower across
the loins than across the chest. The head is rounded, the forehead salient,
and the muzzle somewhat projecting. Both pairs of limbs are much elongated,
the {228}hind-limbs being shorter, however, than the fore-, and the thumb
of the fore-limb is sometimes very rudimentary, being only a nailless
tubercle--or, in the majority of the species, entirely absent, rendering
the hand a much less perfect organ for holding or picking up small objects,
such as fruits, &c.; but its absence probably does not affect, if it does
not even benefit, the hand as an organ for climbing and catching hold again
after a long leap. The nails and other digits of both limbs are compressed,
but much less so than in _Brachyteles_ and _Lagothrix_. The tail is very
long, generally exceeding the length of the body and head, and is nude on
the under side, and very sensitive towards its termination. As a prehensile
organ it has reached the summit of strength and perfection. "It even serves
as a fifth hand, as detached objects, otherwise out of reach, can be
grasped by it, and brought towards the hand or mouth." (_Mivart._) The body
is covered with long, rather coarse, generally black, hair, and has no
woolly under-fur, as in _Lagothrix_ and _Brachyteles_.
With regard to the skeleton of _Ateles_, the lumbar region of the vertebral
column is short, and the dorsal segment attains a greater relative length
than in any other Ape, being over nine-twentieths of the total length of
the spine, without the tail. (_Mivart._) The dorsal and lumbar vertebræ
together number eighteen. In the tail there are twenty-three vertebræ,
flattened on the under side, and exceptionally provided with bony
processes, serving as points for the attachment of muscles for rendering it
as efficient a prehensile organ as possible. The length of the whole arm
and hand in _Ateles_, in proportion to that of the spine, is 174 to 100;
but without the hand it is shorter than the spine, the hand itself being
only slightly shorter than the latter. The proportion of the hind-limb to
the spine is somewhat less, being 169 to 100. The thumb is reduced to a
single metacarpal bone, to {229}which, usually, a single minute nodular
phalanx [finger-bone] is articulated, and is completely hidden beneath the
integument. Although thus rudimentary and functionless, all its
characteristic muscles, except one (the long-flexor) are present.
(_Huxley._) The upper incisors are unequal, the interior being the larger.
There is a space (diastema) between the incisor and the canine teeth (as in
all _Anthropoidea_, except Man); the canines are large and conical; the
upper molars large, and their crowns four-cusped, with transverse ridges
between the outer and inner front cusps and the outer and inner hind cusps,
and also an oblique ridge crossing from the outer front cusp to the inner
hind one. In the larynx of _Ateles_ there is a single median air-sac
opening from the back of the windpipe, but there is no such extension of
the resonating apparatus as is seen in the Howlers (_Alouatta_). In its
brain _Ateles_ exhibits in some respects a higher type than in even the Old
World Apes.
In regard to this group of Monkeys, the late Mr. H. W. Bates made the
following interesting observations:--"In the Coaitas the tail reaches its
highest perfection as a prehensile organ; and on this account it would
perhaps be correct to consider the Coaitas as the extreme development of
the American type of Apes. As far as we know from living and fossil
species, the New World has progressed no further than the Coaita towards
the production of a higher form of the Quadrumanous order. The tendency of
Nature here has been, to all appearance, simply to perfect these organs,
which adapt the species more and more completely to a purely arboreal life;
and no nearer approach has been made towards the more advanced forms of
Anthropoid Apes, which are the products of the Old World solely. The tail
of the Coaita is endowed with {230}a wonderful degree of flexibility. It is
always in motion, coiling and uncoiling like the trunk of an Elephant, and
grasping whatever comes within reach.... The flesh of the Coaitas is much
esteemed by the natives in this part of the country [Obydos, on the
Amazon].... One day I went on a Coaita hunt. When in the deepest part of a
ravine we heard a rustling sound in the trees overhead, and Manoel [the
guide] pointed out a Coaita to me. There was something human-like in its
appearance [which is very characteristic of them], as the lean, dark,
shaggy creature moved deliberately amongst the branches at a great height.
I fired, but unfortunately only wounded it in the belly. It fell with a
crash headlong about twenty or thirty feet, and then caught a bough with
its tail, which grasped it instantaneously, and then the animal remained
suspended in mid-air. Before I could re-load it recovered itself, and
mounted nimbly to the topmost branches out of the reach of a fowling-piece,
where we could perceive the poor thing, apparently probing the wound with
its fingers. Coaitas are more frequently kept in a tame state than any
other kind of Monkey. The Indians are very fond of them as pets, and the
women often suckle them when young at their breasts.[12] They become
attached to their masters, and will sometimes follow them on the ground to
considerable distances.... The disposition of the Coaita is mild in the
extreme; it has none of the painful, restless vivacity of its kindred, the
_Cebi_, and no trace of the surly, untameable temper of its still nearer
relatives, the _Mycetes_, or Howling-Monkeys. It is, however, an arrant
thief, and shows considerable cunning in pilfering small articles of
clothing, which it conceals in its sleeping place."