ORDER OF QUADRUMANA. 
557 
axletrees ; others have assimilated it to the rolling of a drum. 
However correct this simile may be, it is certain there is something 
extremely unnatural about it. Investigation has discovered the 
cause of this strange physiological phenomenon. The hyoid bone 
(the bony ring supporting the larynx) in the Howling Monkey is 
of an immense size ; it is hollow, and forms a kind of drum with 
thin elastic ’walls, which greatly increases the intensity of the 
sounds. This bone occupies an enormous space between the lateral 
branches of the lower jaw, and beneath it constitutes a voluminous 
prominence which is hidden by a thick beard. 
With the Howling Monkeys, or Mycetes, the tail is very long, 
and eminently prehensile. It is hairless on its lower surface 
towards its terminal portion, and to this circumstance owes its 
great sensibility. It is, in reality, a fifth hand, which the animal 
employs with surprising address, either for suspending itself from 
the branches of trees, or to gather fruits and carry them to its 
mouth. 
The grasping power of this tail is sufficiently shown in the 
following trait. The Howling Monkey often darts from a great 
height, and suddenly stops in the middle of its fall by twisting its 
tail around some isolated branch ; it thus balances itself in this 
position for some seconds, and then taking a new spring, it carries 
itself to a neighbouring limb. Sometimes one of these Monkeys, 
shot dead, remains suspended by the tail, and thus disappoints 
the hunter in search of its flesh or fur. 
The Howlers are dull and ferocious. Reduced to confinement, 
they lose their voice, decline, and die. In a wild state, they con- 
gregate in small bands, under the leadership of an experienced 
male, who is entrusted with all the arrangements relative to the 
general safety. Although timid, they readily allow themselves to 
be approached ; but if they discover any hostile intention, they 
flee with rapidity from the intruder. 
Certain authors have asserted that the females of the Mycetes 
are devoid of maternal sentiment, and that they abandon their 
young in order to fly more quickly if menaced by danger. Never- 
theless, all travellers do not think so. Spix was witness to a 
touching incident to the contrary. He had mortally wounded 
a female, who carried her progeny on her back. The poor parent 
fell from branch to branch, and the young one would undoubtedly 
