Humboldt saw them in the great virgin forests of Brazil, hanging in curious clusters, clasping each other by means of their limbs and tails, and all being suspended by the tail of one strong fellow. He was, as everybody must be, greatly impressed with their clever use of their tails, for he observed them being used as a fifth member, and with all the dexterity of hands. The natives will have it that they fish with their tails, but this is of course untrue, and they do not carry anything to their mouths with them. They are wonderful swingers and claspers, and they are exquisitely sensitive at the tip and for some inches underneath it, and they are stout where they join the body, exceedingly muscular, and in some kinds there are long hairs on them, especially near the end. These Monkeys have small heads, long necks, and exceedingly long arms and legs; some are covered with a soft fur, and in others it is harsh, and the hairs are long and rigid; and all have the thumbs of the hands either absent or just visible as slight projections. The feet are long and have well-shaped toe-thumbs. Their head is round, and the muzzle only projects slightly, so that there is something human in their appearance, especially when their large eyes are open; and the hair in some kinds is brushed forwards on the cheeks and brows so as to resemble whiskers and front hair. There is something in their shape, without the tail, which reminds one of the Gibbons, those long-armed Apes of the East, and the fore-hands resemble those of the Colobi of Africa (page 100); but the Spider Monkeys have not the power of jumping possessed by these, and their hind legs, useful as they are when amidst the great trailing orchids and the climbers of the American tropics, are feeble members when on the ground. Then the Monkey walks on the outside edge of the feet, and on the inside edge of the hand, with its tail feeling here and there for anything to catch hold of. Often they are very sedate and slow in their movements, like the Semnopitheci of India, and they indulge in a series of climbings from bough to bough, swinging from one to the other, and holding on now and then and assisting in the movement with the tail. They are as gentle in their manners as those just mentioned, and are full of play with each other. Their teeth resemble those of the Howlers, but the eye teeth, or canines, are smaller, and the crushing teeth, or molars, are rounder. From the defective thumbs, all these Monkeys as a group or genus have been termed “imperfect-handed,” and therefore two Greek words which convey these terms ἀτελής (imperfect), and χείρ (the hand), have been conjoined in the word Atelochirus, of which Ateles is used as an abbreviation. [Illustration: GROUP OF SPIDER MONKEYS.]