SPIDER-MONKE YS. 
iS9 
tail, with the naked parts of the face flesh-coloured; 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 colour, with white on the sides of the face. 
THE WOOLLY SPIDEILMONKEY (J liat. size). 
The Spider-Monkeys. 
Genus Aides. 
The spider-monkeys may be regarded as those members of the group most 
admirably 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 ( Colobus) 
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. 
