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 flat 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 (H. 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 (H. variegatus) appears to be 

 but another of the numerous varieties of H. agilis. 



THE Wou-Wou, OR 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 bluish- 

 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. 



VOL. I. 5 



