Page:Quarterly Journal of the Geological Society of London, vol. 25.djvu/245

1869.] HUXLEY— HYPERODAPEDON. 151 its most characteristic birds are the giant Dinornithidoe, some of which were competent to keep stride with the Brontozoum itself.

What if this present New Zealand fauna, so remarkable and so isolated from all other faunae, should be a remnant, as it were, of the life of the Poikilitic period which has lingered on isolated, and therefore undisturbed, down to the present day?

I am quite aware that a host of difficulties may be opposed to this suggestion; but these all seem to me to be rather of the nature of questions which cannot be answered for want of information, than of objections formidable in themselves. For example, mammals existed in the Poikilitic epoch. Why did none of these inhabit the New-Zealand area and survive to the present day? Again, how comes it that the solitary amphibian of New Zealand is a Frog allied to those of South America, and not a Labyrinthodont? And why are the freshwater fishes also allied to, and, in one case, specifically identical with those of South America*, instead of resembling Triassic Ganoids?

I cannot give a direct answer to these questions, but I can show that analogous difficulties exist in cases where there can be no sort of doubt as to the origin of a fauna. Thus there can be no doubt that the fauna of Ireland is derived from the same source as that of Europe; but just as New Zealand is devoid of the class Mammalia, so is, or was, Ireland devoid of the class Reptilia; again, there is no indigenous British Ganoid or Siluroid freshwater fish, though both occur in the rivers of Central and Eastern Europe.

May it not be possible that causes similar to those which have shut out whole groups of Vertebrata of the European fauna of the present epoch from the British region, operated upon New Zealand in the Poikilitic period and caused its fauna to represent only a fraction of that of neighbouring lands? Or may it not be possible that causes such as those which determined the extinction of the indigenous horse, Macrauchenia, Toxodon, Glyptodon, &c. of South America, while they left multitudes of other genera alive, have similarly weeded down the fauna of New Zealand, and that investigations in the caves and superficial deposits of that country will yield forms which now no longer exist there?

I mention these possibilities simply for the purpose of showing how much greater value attaches to the positive similarities between the New-Zealand Fauna and that of the Trias than to their negative differences.

Finally, I may remark upon the complete modification of former ideas respecting the supposed poverty of life during the Poikilitic epoch which has been effected by the discoveries of late years.

It is now clear that all the five classes of the Vertebrata, viz. Mammalia, Aves, Reptilia, Amphibia, and Pisces, were represented at this epoch. The mammals were apparently Marsupials, not Monotremes. Of the birds nothing is known. Of reptiles, we have Dinosauria, Crocodilia, Dicynodonts, Lacertilia of several forms, Ple-

Gunther, F.R.S.
 * I state these remarkable distributional facts on the high authority of Dr.