If now we review the evidence adduced, and select the more important points we find in the distribution of the Struthious birds, the frogs, freshwater fishes, several shells (such as Cyclina kroyeri, Mytilus magellanicus, Anomia alecto, Barbaia pusilla, Chione stutchburyi, and Ranella vexillum), in the genus Hemicops among the Centipedes, and Perripatus among the Annelids, evidence of a former great extension of land in the Southern Hemisphere, for these cases cannot all be accounted for by drifting icebergs. With the exception of the shells and two fresh-water fishes no species however is common to New Zealand and South America on the one hand, nor to New Zealand and South Africa on the other, for I omit from consideration the species of marine fish, as they might perhaps have crossed at a later date. In the frogs the genera, and in the birds the families, are different. This perhaps indicates a very long interval since the separation of these countries took place, but differentiation of form, even in closely allied species, is evidently a very fallacious guide in judging of lapse of time, and a surer one is afforded us in the absence of Mammalia from New Zealand, for it is evident that if the Marsupials that now inhabit Australia, or the placental Mammals that inhabit South America, had been in existence at the time of the distribution of the Struthious birds some members would have found their way to New Zealand, and would have remained upon it with the Moas. This antarctic continental period must therefore have preceded the spread of the Mammalia into the Southern Hemisphere. Besides this continental period we have evidence in Eudynamis taitiensis, Naultinus pacificus, Amphibola avellana, Musca taitensis, and in the genera Ocydromus and Nestor, of a Polynesian continent quite unconnected with Australia, but including Lord Howe Island, Norfolk Island, and New Caledonia, while by Helix coniformis, H. rapida, H. radiaria and H. vitrea, we can prove a close connection with the New Hebrides, Solomon Islands, Louisade Archipelago, and the Admiralty Islands. By Nanina among land shells, and Assiminea among fresh-water shells, we prove a connection also with the Navigator and Friendly Islands, and these genera take us north through the Molucca Islands, Celebes, Borneo and the Philippines, to China, where we again come across many New Zealand species and genera. The
most important are Ditrema, Torpedo, and Anguilla latirostris among fishes; Mytilus smaragdinus, Phorus, Rotella, Calyptræa, Cassidula mustilina, Lymnæa, and Rhynchonella among shells; Perla and Hermes among insects; Lithobius among centipedes; Bipalium among the Scolecida, and Pentagonaster pulchellus and Othilia luzonica among the star-fish; none of these, it must be remembered, being found in Australia. The absence of Mammalia, however, in New Zealand shows that this line of communication was never continuous land, but the absence from Australia of the forms that I have mentioned shows that the connection along the whole line was closer at every point than it was with that continent, and this leads to the further conclusion that this line of communication existed at a later date than the connection of New Zealand with Australia.
The close relationship of the Chatham and Auckland Islands in all their natural productions to those of New Zealand, and the far greater difference between New Zealand and the islands more to the north, as well as the large number of species of moa lately inhabiting these islands, shows that another and smaller continent, or perhaps a large island, existed at a still later period, but has since subsided, and this must bring us nearly to the recent period, or the difference between New Zealand and the Chatham Islands would be greater.
The geographical distribution, therefore, of the New Zealand fauna points to the following conclusions:—
1. A continental period, during which South America, New Zealand, Australia, and South Africa were all connected, although it is not necessary that all should have been connected at the same time, but New Zealand must have been isolated from all before the spread of the Mammals, and from that time to the present it has never been completely submerged. This continent was inhabited by Struthious birds, and by Hymenolaimus, Notornis, Hinulia, Mocoa, Galaxias, Prototroctes, Liopelma, Janella, Amphibola, Hemicops, and Peripatus, and further to the north by Megapodius; and probably also by many forms peculiar to New Zealand, such as Stringops, Keropia, Xenicus, Heteralocha, Anarhynchus, Naultinus, etc. Of course in mentioning these names I do not mean that all the forms were the same then as now, but that the ancestors of these genera lived on the old antarctic continent.
2. Subsidence followed, and the evidence then points to a second continent stretching from New Zealand to Lord Howe Island and New Caledonia, and extending for an unknown distance into Polynesia, but certainly not so far as the Sandwich Islands. The fact of Mammals being found in the New Hebrides, Solomon Islands, and New Ireland, shows that between New Caledonia and the New Hebrides a narrow strait must have existed, cutting off land communication, but these were connected with China either direct or
by a chain of islands. This second continent received from the north those forms already enumerated together probably with Sphenæacus, the rails, and the starlings; at the same time it received from Australia the honey-eaters, Certhiparus, Gerygone, Petroica, Rhipidura and others, and from that time to the present has been occasionally receiving additional birds. It will also be noticed that very few of the birds of the middle palæotropical region came down this line of communication, no pheasants, woodpeckers, grackles nor finches, while Australia in its wood-swallows (Artamus), pittas, quails, and numerous finches, shows now some affinity to this region. This can be best explained by supposing that the New Zealand line of communication was broken up before these birds came into existence, and that further changes have since taken place in the lines of easiest communication; indeed, the fact of such forms as the elephant, tiger, and bear being found in Sumatra and Borneo; Marsupials in Celebes, the Moluccas, Solomon Islands, and New Hebrides; and the presence of an emu in New Guinea, and a cassowary in Australia, prove that changes in the distribution of land have since taken place, but it is foreign to the object of this paper to speculate on these here. This second continent was also inhabited by most of the orders of insects, although perhaps not in great abundance, but Heteroptera and the butterfly section of the Lepidoptera were absent.
3. Subsidence again followed, and New Zealand was reduced for a long time to a number of islands, upon many of which the moa lived. This was followed by—
4. Elevation; these islands were connected and a large island existed disconnected from Polynesia. This was once more followed by—
5. Subsidence, and the geography of this part of the World assumed somewhat of its present form.