710 REPORT— 1884. 



and so uniform is this throughout that no separate regions can he established, so 

 that there is but one oceanic to contrast with 14 terrestrial regions. 



It is impossible to enter further into this subject now, and I can only allude to 

 the evidence in favour of the existence of land-regions in past times. It is scarcely- 

 necessary to remind you of the proofs already accumulated of differences between 

 the fauna of distant countries in Tertiary times. The Eocene, Miocene, and 

 Pliocene vertebrata of North America differ quite as much from those of Europe 

 in the same periods as do the genera of the present day ; and there was as much 

 distinction between the mammalia of the Himalayas and of Greece when the 

 Siwalik and Pikermi faunas were living as there is now. In Mesozoic times we 

 have similar evidence. The reptiles of the American Jurassic deposits present 

 wide differences from those of the European beds of that age, and the South 

 African reptilian types of the Karoo beds are barely represented elsewhere. But 

 there is no reason for supposing that the limits or relations of the zoological and 

 botanical regions in past times were the same as they now are. It is quite certain 

 indeed that the distribution of land-areas, whether the great oceanic tract has re- 

 mained unchanged in its general outlines or not, has undergone enormous variations,. 

 and the migration of the terrestrial fauna and flora must have been dependent 

 upon the presence or absence of land communication between different continental 

 tracts ; in other words, the terrestrial regions of past epochs, although just as clearly 

 marked as those of the present day, were very differently distributed. The re- 

 markable resemblance of the floras in the Karoo beds of South Africa, the Damuda 

 of India, and the coal-measures of Australia, and the wide difference of all 

 from any European fossil flora, is a good example of the former distribution of life ; 

 whilst it is scarcely netessary to observe that the present Neotropical and Australian 

 mammals resemble those of the same countries in the later Tertiary times much 

 more than they do the living mammalia of other regions, and that the Australian 

 mammal fauna is in all probability more nearly allied to the forms of life inhabit- 

 ing Europe'in the Mesozoic era than to any European types of later date. If the 

 existing mammals of Australia had all become extinct, a deposit containing their 

 bones would probably have been classed as Mesozoic. 



The belief in the former universality of faunas and floras is very much con- 

 nected with the idea once generally prevalent, and still far from obsolete, that the 

 temperature of the earth's surface was formerly uniform, and that at all events- 

 until early or even middle Tertiary times the poles were as warm as the equator, 

 and both enjoyed a constant tropical climate. The want of glacial evidence from 

 past times in Spitzbergen and Greenland, where a temperature capable of support- 

 ing arboreal vegetation has certainly prevailed during several geological periods, is 

 counterbalanced by the gradually accumulating proofs of Lower Mesozoic or Upper 

 Palaeozoic glacial epochs in South Africa, Australia, and, strangest of all, in India. 

 Even during those periods of the earth's history when there is reason to believe 

 that the temperature in high latitudes was higher than it now is, evidence of distinct 

 zones of climate has been observed, and quite recently Dr. Neumayr, 1 of Vienna, 

 has shown that the distribution of Cretaceous and Jurassic cephalopoda through- 

 out the earth's surface proves that during those periods the warmer and cooler 

 zones of the world existed in the same manner as at present, and that they 

 affected the distribution of marine life as they do now. 



The idea that fresh-water and terrestrial faunas and floras were similar throughout 

 the world's surface in past, times is so ingrained in palaeontological science that it 

 will require many years yet before the fallacy of the assumption is generally 

 admitted. No circumstance has contributed more widely to the belief than the 

 supposed universal diffusion of the Carboniferous flora. The evidence that the 

 plants which prevailed in the coal-measures of Europe were replaced by totally 

 different forms in Australia, despite the closest similarity in the marine inhabitants 

 of the two areas at the period, will probably go far to give the death-blow to an 

 hypothesis that rests upon no solid ground of observation. In a vast number 



1 ' TJeber klimatische Zonen wahrend der Juras- und Kreidezeit,' Dentochr. Math, 

 Net. CI. Akad. Wins. Wien, vol. xlvii. 1883. 



