SPIDER-MONKEY, the English title of a group of tropical American monkeys known to the natives of Brazil by the name coaita, and to zoologists as Ateles, in allusion to the imperfectly-developed thumb. They take their English name from the slimness of the body, the elongated limbs, and the long tail, the under surface of the prehensile extremity of which is naked. The thumb is either rudimentary or wanting, so that the hands act merely as hooks in climbing. The absence of woolly under-fur, the less compressed nails, and the broader partition between the nostrils distinguishes them from the woolly spider-monkeys (Brachyteles.) The species are numerous, and the most active and thoroughly arboreal of all American monkeys. The prehensile tail is employed not only as a means of suspension, but also to convey food to the mouth. These monkeys generally go about in small parties, high up in the trees; and, like the other members of the group, are comparatively silent. Their food consists chiefly of fruits and leaves. (See Primates.)