GIBBONS. 
65 
feet of the same general colour as the body. It may be distinguished by the 
prominent arches on the skull above the eyes, the comparatively hat nose, and the 
large nostrils. The colour of the back in the darker varieties is lighter than that 
of the under parts. The variety named after Sir Stamford Raffles, H. rafflesi, 
is of a nearly black colour, tending to brown on the sides and back. The 
Siamese variety, known as the crowned or tufted gibbon (II. pileatus), is likewise 
of a blackish colour, but differs in that the hands, feet, and a ring round the crown 
of the head are white. The white patch on the crown helps to distinguish this 
variety from the typical agile gibbon; although it must be confessed that all these 
Malay gibbons are singularly alike, and often difficult to distinguish even by the 
practised zoologist. This so-called variegated gibbon (II. variegatus ) appears to be 
but another of the numerous varieties of H. agilis. 
The Wou-Wou, oh Silver Gibbon (Hylobates leuciscus). 
The grey or silver gibbon, or wou-wou,—a name often incorrectly applied to 
the agile gibbon,—comes from the island of Java, and most zoologists agree in 
regarding it as a distinct species. It is characterised by its general ashy or bluisli- 
grey colour; the presence of a large square black patch on the top of the head; 
and also by the white or grey fringe of hair surrounding the blackish face. The 
fur also appears to be longer, thicker, and of a more woolly nature than is the case 
in the other species; and the colour is stated to be usually lighter on the under 
parts than on the back. Specimens of both this and the preceding species have 
been exhibited in the London Zoological Society’s Gardens. 
Fossil Gibbons. 
In the explorations which have been conducted in the caves of Borneo remains 
of gibbons, probably belonging to species still existing in the same regions, have 
been met with in a sub-fossil condition. This is only what we should naturally 
have expected to be the case. Very different, however, is the occurrence of fossil 
gibbons in fresh-water strata belonging to the middle portion of the Tertiary 
period in France and Switzerland; for it is quite certain that these animals could 
not have existed in a climate at all approaching that now characterising Europe. 
We shall, therefore, be safe in assuming that, at the period in question, portions of 
Southern Europe were clothed with dense forests, growing in a hot and moist 
climate closely resembling that of the Malay Archipelago of the present day. The 
evidence for the former prevalence of this tropical European climate does not, 
however, rest solely on the fossil gibbons, since many of the other animals found 
in the same strata are very similar to those now characteristic of the warmer 
regions of the East; while the presence of palms, resembling those of tropical 
regions, as well as other plants, supplements the evidence of the animals in a 
manner which must be convincing to all who pay any attention to the subject. 
After the middle or miocene division of the Tertiary period we have no evidence 
of the existence of gibbons in any part of Europe, although many kinds of 
monkeys were abundant until much later. 
