HuTTON. — The Geological History of Nciv Zealand. 177 



Lastly comes the question, When did this elevation take 

 place? I will take the biological evidence first. The great 

 similarity between the faunas and floras of the two Islands of 

 New Zealand shows undoubtedly that they were once united ; 

 and an elevation of 500 ft. at Cook Strait would connect them 

 again. Nevertheless, we find six different kinds of birds 

 represented by different species in each Island ; and this is 

 not due to differences in climate or in the physical features of 

 the two Islands, but to changes in the animals which have 

 taken place since the Islands were separated. It is the same 

 with the extinct moas. Nearly all — perhaps all — of the 

 known species were confined to one or other of the Islands, 

 and certainly none were abundant in both. But this implies 

 that the Islands have been separated by Cook Strait for a long 

 time, during which, of course, there could have been nO' 

 general elevation. 



Still, as I said before, it is evident that the two Islands 

 were once united. Indeed, we may go further and say that 

 in all probability the Chatham Islands, the Auckland Islands, 

 and perhaps Campbell and Macquarie Islands were at one 

 time united to New Zealand by land, for their faunas and 

 floras ai'e closely allied to those of New Zealand, and are 

 quite unlike those of Tasmania. 



As no lizards nor land-shells have passed between Tas- 

 mania and New Zealand, and as very few birds, insects, and 

 plants are common to both countries, although the distance 

 between them is not much more than twice that between 

 New Zealand and the Chatham Islands, it is evident that our 

 connection with these and wdth the Auckland Islands must 

 formerly have been much closer than it is now. And the pre- 

 sence of a slug common to all three suggests that there was a 

 land-communication between them. 



Now, these outlying islands contain many endemic species 

 of plants and animals, and, in the case of the Chatham Is- 

 lands, we cannot explain the existence of these distinct 

 species by differences of climate. Out of twenty-one land- 

 birds on the Chathams, seven — that is, one-third of the 

 whole — are endemic. And of the plants about 15 per cent. 

 are endemic. This implies that the Chatham Islands have 

 been isolated for a very long time, and we can say with some 

 confidence that this isolation must have lasted ever since the 

 close of the Pliocene period. But when New Zealand ex- 

 tended so far as to include the Chatham Islands it probably 

 stood at a much higher elevation than at present ; and the 

 Pliocene period, therefore, is the time we should expect that 

 the greatest extension of our glaciers took place. 



We will now take the geological evidence. In the first 

 place, it is significant that there are no marine Pliocene beds 

 12 



