812 ANIMALS OF EGA. Chap. Y. 
scarlet-face was missing, having made his escape into 
the forest Two men were sent in search of him, but 
retm^ned after several hours' absence without having 
caught sight of the runaway. We gave up the monkey 
for lost^ until the following day, when he re-appeared on 
the skirts of the forest, and marched quietly down the 
bowsprit to his usual place on deck. He had evidently 
found the forests of the Rio Negro very different from 
those of the delta lands of the Japura, and preferred 
captivity to freedom in a place that was so uncongenial 
to him. 
A most curious fact connected with this monkey is 
the existence of an allied form, or brother species, in a 
tract of country lying to the west of its district. This 
differs in being clothed with red instead of white hair, 
and has been described by Isidore Geoffrey St. Hilaire 
(from specimens brought to Paris in 1847 by the Comte 
de Castlenau) as a distinct species, under the name of 
Brachyurus rubicundus. It wholly replaces the white 
form in the western parts of the Japura delta : that is 
to say, in a uniform district of country, 150 miles in 
length, and sixty to eighty in breadth, the eastern half 
is tenanted exclusively by white Uakaris, and the 
western half by red ones. The district, it may be men- 
tioned, is crossed by several channels, which at the 
present time doubtless serve as barriers to the dispersal 
of monkeys, but cannot have done so for many centuries, 
as the position of low alluvial lands, and the direc- 
tion of channels in the Amazons Valley, change con- 
siderably in the course of a few years. The red-haired 
Uakari appears to be most frequently found in the 
