THE YELLOJV-TAILEB HOWLER. 
167 
They have rather tall heads, with beard and large lower jaws, which, with a thickness about the 
throat, give the appearance of an unusual swelling being there, the cause of which will be noticed 
further on. Some have long and others short fur, but generally there is much of it about the head 
(where it is brushed forwards) and neck. Black and red are favourite colours, and the young of both 
sexes differ often in their tints from the adults, and so do the males from the females. One kind in 
particular is decidedly coloured. 
THE YELLOW-TAILED HOWLER.'* 
The last half of the tail of this species is of a brilliant golden-fawn colour, and this tint is on 
the upper parts of the body nearly up to the shoulders ; the rest of the tail is light maroon, and what 
remains of the body is dark maroon, there being a violet tint in the limbs. 
Besides its colours this kind presents some points of interest. They live in companies, and when 
they pass from one tree to another they all play at folio w-my -leader exactly. They watch the move- 
ments of those which precede them, jump in the same maimer, and at the same place, and even place 
their feet and hands on the same spots on the boughs. They are found in Columbia and New Granada, 
and in Brazil on the confines of Paraguay. 
The limbs of all the Mycetes are long, and whilst there is a good toe-tlmmb to the foot, the very 
best of the hand-thumbs is not equal to those of the Monkeys of the Old World. The nails on the 
fingers and toes are compressed from side to side, as it were, and begin to look like claws. 
Ogilby, an admirable observer, noticed years ago that two Howlers did not use their hands so as 
to take things between the thumb and forefinger, and he ascertained that this thumb was so much on 
a line with the other fingers that it was not opposable in the ordinary sense of the word, and that it 
was more like an extra finger than a thumb. This, he noticed, was not the case with the Howlers 
alone, but that it peculiarised the Monkeys of the New World, 
skeletons shows that the bones of the thumb are on the same 
plane or level as tl*e fingers, and the whole is brought close to 
the fingers, as our great toe is to the other toes. Nevertheless, 
this thumb can move to and from the fingers. 
But if the fore-hand so greatly resembles a paw, compensation 
is made to the animal by the gift of the prehensile tail, which is 
very muscular, and the under surface is without hair near the 
end, so that the sensitive surface can touch and feel objects. They 
•can feel, therefore, around them, and also above them, as they 
move along and lay hold of branches and hanging creepers without 
looking for them. The delicate sense of feeling depends on the 
nervous supply ; and the power of clasping and holding on upon 
the bending or flexor muscles. A bony framework supports all 
these structures, and runs from the last bone of the sacrum to 
the tip, and consists of many separate vertebral bones' placed in a 
The examination of their 
sacrum, boxes or the tail or the howler. 
processes for jointing with the 
long series. The first few bones which join on to the 
and form the root of the tail, resemble the back-bone pieces, 
or vertebrae, to a certain extent. Each has a body, and also 
one before and behind, and a spine also. Besides these, there are two curious projections on 
the lower part of each body, which are called chevron bones, and are Y-shaped, and their use is to 
allow the blood-vessels and nerves to pass along between them without being pressed upon. Towards 
the end of the tail the vertebrae become long and stout, and are united behind and in front, forming a 
broad bone, and without the joints, and the chevron bones are reduced to little rounded pieces of bone. 
Everything tends in this tail to ready, rapid, and forcible motion, and indeed so perfect an organ is 
it that when one of these Howlers is shot it always hangs to the tree by its tail, even if quite dead, 
and does not fall down until some hours afterwards, when the strong flexor muscles have relaxed 
# Mycetes chrysum. 
