32 THE POPULAR SCIENCE MONTHLY. 



few words on their general relations as a distinct order of mammalia. 

 No other group, so extensive and so varied as this, is so exclusively 

 tropical in its distribution, a circumstance no doubt due to the fact 

 that monkeys depend so largely on fruit and insects for their subsist- 

 ence. A very few species extend into the warmer parts of the tem- 

 perate zones, their extreme limits in the northern hemisphere being 

 Gibraltar, the western Himalayas at eleven thousand feet elevation, 

 East Thibet, and Japan. In America they are found in Mexico, but 

 do not appear to pass beyond the tropic. In the southern hemisphere 

 they are limited by the extent of the forests in South Brazil, which 

 reach about 30 south latitude. In the East, owing to their entire 

 absence from Australia, they do not reach the tropic ; but in Africa 

 some baboons range to the southern extremity of the continent. 



But this extreme restriction of the order to almost tropical lands is 

 only recent. Directly we go back to the Pliocene period of geology, 

 we find the remains of monkeys in France, and even in England. In 

 the earlier Miocene several kinds, some of large size, lived in France, 

 Germany, and Greece, all more or less closely allied to living forms of 

 Asia and Africa. About the same period monkeys of the South 

 American type inhabited the United States. In the remote Eocene 

 period the same temperate lands were inhabited by lemurs in the East, 

 and by curious animals believed to be intermediate between lemurs 

 and marmosets in the West. We know from a variety of other evi- 

 dence that throughout these vast periods a mild and almost sub-trop- 

 ical climate extended over all Central Europe and parts of North 

 America, while one of a temperate character prevailed as far north as 

 the Arctic Circle. The monkey-tribe then enjoyed a far greater range 

 over the earth, and perhaps filled a more important place in Nature 

 than it does now. Its restriction to the comparatively narrow limits 

 of the tropics is no doubt mainly due to the great alteration of climate 

 which occurred at the close of the Tertiary period, but it may have 

 been aided by the continuous development of varied forms of mam- 

 malian life better fitted for the contrasted seasons and deciduous vege- 

 tation of the north temperate regions. The more extensive area 

 formerly inhabited by the monkey-tribe would have favored their 

 development into a number of divergent forms, in distant regions and 

 adapted to distinct modes of life. As these retreated southward and 

 became concentrated in a more limited area, such as were able to 

 maintain themselves became mingled together as we now find them, 

 the ancient and lowly marmosets and lemurs subsisting side by side 

 with the more recent and more highly developed howlers and anthro- 

 poid apes. 



Throughout the long ages of the Tertiary period monkeys must 

 have been very abundant and very varied, yet it is but rarely that 

 their fossil remains are found. This, however, is not difficult to ex- 

 plain. The deposits in which mammalian remains most abound are 



