228 ALLEN’S NATURALIST’S LIBRARY. 
limbs being shorter, however, than the fore-, and the thumb of 
the fore-limb is sometimes very rudimentary, being only a nail- 
less 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 nudz on the under side, and very sensitive towards its 
termination. Asa prehensile organ it has reached the summit 
of strength and perfection. ‘““TIt 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.” (A/7vart.) The 
body is covered with long, rather coarse, generally black, hair, 
and has no woolly under-fur, as in Lagothrix and Lrachyteles. 
With regard to the skeleton of AZe/es, the lumbar region of the 
vertebralcolumn is short, and the dorsal segment attains agreate1 
relative length than in any other Ape, being over nine-twentieths 
of the total length of the spine, without the tail. (AZzvar?¢.) The 
dorsal and lumbar vertebre together number eighteen. In the 
tail there are twenty-three vertebrze, 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 Afe/es, 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 propor- 
tion of the hind-limb to the spine is somewhat less, being 169 
to 100. The thumb is reduced to a single metacarpal bone, to 
