THE SPIDER-MONKEYS 



159 



these are merely varieties of a single species (Eriodes arachnoides), since some indi- 

 viduals have a rudiment of a thumb on one hand and not a trace of one on the 

 other. In the typical variety, as represented in our illustration, the general color 

 is ashy brown, often tending to ferruginous at the base of the root of the tail, 

 with the naked parts of the face flesh colored ; the females being of a paler hue. 

 The thumb is totally wanting. Another variety, with a distinct rudiment of a 

 thumb, is of a dark brown color, with white on the sides of the face. 



THE SPIDER- MONKEYS 

 Genus A teles 



The spider-monkeys may be regarded as those members of the group most ad- 

 mirably adapted for a purely arboreal life, as is especially shown by their slight 

 bodies, the long prehensile tail, naked below at the end, and the long spider-like 

 limbs from which they derive their popular title. In the rudimentary condition, or 

 total absence, of their thumbs, the spider-monkeys may be regarded as holding the 

 same relationship to the sapajous as is presented by the thumbless monkeys {Colo- 

 bus} of Africa to the langurs (Semnopithecus*) of India ; and it is probable that in 

 both instances the abortion of the thumb is due to the uselessness of this digit in a 

 hand adapted to act merely as a kind of hook in swinging from branch to branch. 



In general characteristics the true spider-monkeys agree with the woolly spider- 

 monkeys, but are readily distinguished from them by the total absence of a woolly 

 under-fur, the comparatively slight degree of compression in the nails, and the 

 greater width of the partition between the nostrils ; the thumb being generally ab- 

 sent. They are, moreover, of far more active habits, and in this respect are only 

 equaled by the langurs and gibbons of the Old World, over which they have the 

 advantage of the prehensile tail. To the description quoted from Waterton on p. 

 145, in which these monkeys are especially referred to, it may be added that they 

 not unfrequently use this tail to convey fruit and other articles of food to their 

 mouths. Those who have seen spider-monkeys swinging from rope to rope and 

 leaping from side to side of their cages in menageries, can, when the cage is suffi- 

 ciently large, gain some idea of their marvelous activity, although in such confined 

 spaces their movements bear no comparison to what they are when in the boundless 

 freedom of their native forests. 



It is noteworthy that the stomachs of the spider-monkeys have a trace of the 

 sacculated condition which distinguishes those of the long-limbed and long-tailed 

 langurs and thumbless monkeys of the Old World. Their fur is generally smooth 

 and stiff ; and, as a rule, the hair on the crown of the head is directed forward. 



The number of species of spider-monkeys is very large, and we shall thus be 

 compelled to limit our notice to some of the better-known types. The genus has a 

 wide geographical range, extending from Uruguay in the south to southern Mexico 

 in the north. 



