New Caledonia, and the New Hebrides.—Although these islands seem best placed with Polynesia, yet they form a transition to Australia proper, and to the Papuan group. They possess 30 genera of land-birds, 18 of which are typical of the Australian region; but while 13 are also Polynesian, there are 5 which do not pass further east. These are Acanthiza, Eopsaltria, Gliciphila, Philemon, and Ianthœnas. The peculiar Polynesian genus, Aplonis, of which three species inhabit New Caledonia, link it to the other portions of the sub-region. The following are the genera at present known from New Caledonia:—Turdus, Acanthiza, Campephaga, Lalage, Myiagra, Rhipidura, Pachycephala, Eopsaltria, Corvus, Physocorax (s.g. of Corvus, allied to the jackdaws), Glicphila, Anthochæra, Philemon, Zosterops, Erythrura, Aplonis, Artamus, Cuculus, Halcyon, Collocalia, Cyanoramphus, Trichoglossus, Ptilopus, Carpophaga, Macropygia, Ianthœnas, Chalcophaps, Haliastur, Accipiter. The curious Rhinochetus jubatus, forming the type of a distinct family of birds (Rhinochetidæ), allied to the herons, is only known from New Caledonia.

It thus appears, that not more than about 50 genera and 150 species of land-birds, are known from the vast number of islands that are scattered over the Central Pacific, and it is not probable that the number will be very largely increased. Some of the species, as the Eudynamis taitensis and Tatare longirostris, range over 40° of longitude, from the Fiji Islands to the Marquesas. In other genera, as Cyanoramphus and Ptilopus, each important island or group of islands, has its peculiar species. The connection of all these islands with each other, on the one hand, and their close relation to the Australian region, on the other, are equally apparent; but we have no sufficient materials for speculating with any success, on the long series of changes that have brought about their existing condition, as regards their peculiar forms of animal life.

Sandwich Islands.—This somewhat extensive group of large islands, is only known to contain 11 genera and 18 species of indigenous land-birds; and even of this small number, two birds of prey are wide ranging species, which may well have reached the islands during their present isolated condition. These latter are, Strix delicatula, an owl spread over Australia and the Pacific; and Asio accipitrinus, a species which has reached the Galapagos from S. America, and thence perhaps the Sandwich Islands. Of the remaining 8 genera, one is a crow (Corvus hawaiensis), and another a fishing eagle (Pandion solitarius), of peculiar species; leaving 7 genera, which are all (according to Mr. Sclater) peculiar. First we have Chasiempis, a genus of Muscicapidæ, containing two species (which may however belong to distinct genera); and as the entire family is unknown on the American continent these birds must almost certainly be allied to some of the numerous Muscicapine forms of the Australian region. Next we have the purely Australian family Meliphagidæ, represented by two genera,—Moho, an isolated form, and Chætoptila, a genus established by Mr. Sclater for a bird before classed in Entomyza, an Australian group. The four remaining genera are believed by Mr. Sclater to belong to one group, the Drepanididæ, altogether confined to the Sandwich Islands. Two of them, Drepanis and Hemignathus, with three species each, are undoubtedly allied; the other two, Loxops and Psittirostra, have usually been classed as finches. The former seem to approach the Dicæidæ; and all resemble this group in their coloration,

The aquatic birds and waders all belong to wide-spread genera, and only one or two are peculiar species.

The Sandwich Islands thus possess a larger proportion of peculiar genera and species of land-birds than any other group of islands, and they are even more strikingly characterised by what seems to be a peculiar family. The only other class of terrestrial animals at all adequately represented on these islands, are the land shells; and here too we find a peculiar family, sub-family, or genus (Achatinella or Achatinellidæ) consisting of a number of genera, or sub-genera,—according to the divergent views of modern conchologists,—and nearly 300 species. The Rev. J. T. Gulick, who has made a special study of these shells on the spot, considers that there are 10 genera, some of which are confined to single islands. The species are so restricted that their average range is not more than five or six square miles, while some are confined to a tract of only two square miles in extent, and very few range over an entire island. Some species are confined to the mountain ridges, others to the valleys; and each ridge or valley possesses its peculiar species. Considerably more than half the species occur in the island of Oahu, where there is a good deal of forest. Very few shells belonging to other groups occur, and they are all small and obscure; the Achatinellæ almost monopolising the entire archipelago.

Remarks on the probable past history of the Sandwich Islands.—The existence of these peculiar groups of birds and land-shells in so remote a group of volcanic islands, clearly indicates that they are but the relics of a more extensive land; and the reefs and islets that stretch for more than 1,000 miles in a west-north-west direction, may be the remains of a country once sufficiently extensive to develope these and many other, now extinct, forms of life.[[16]]

Some light may perhaps be thrown on the past history of the Sandwich Islands, by the peculiar plants which are found on their mountains. The peak of Teneriffe produces no Alpine plants of European type, and this has been considered to prove that it has been always isolated; whereas the occurrence of North Temperate forms on the mountains of Java, accords with other evidence of this island having once formed part of the Asiatic continent. Now on the higher summits of the Sandwich Islands, nearly 30 genera of Arctic and North Temperate flowering plants have been found. Many of these occur also in the South Temperate zone, in Australia or New Zealand; but there are others which seem plainly to point to a former connection with some North Temperate land, probably California, as a number of islets are scattered in the ocean between the two countries. The most interesting genera are the following:—Silene, which is wholly North Temperate, except that it occurs in S. Africa; Vicia, also North Temperate, and in South Temperate America; Fragaria, with a similar distribution; Aster, widely spread in America, otherwise North Temperate only; Vaccinium, wholly confined to the northern hemisphere, in cold and temperate climates. None of these are found in Australia or New Zealand; and their presence in the Sandwich Islands seems clearly to indicate a former approximation to North Temperate America, although the absence of any American forms of vertebrata renders it certain that no actual land connection ever took place.

Recent soundings have shown, that the Sandwich Islands rise from a sea which is 3,000 fathoms or 18,000 feet deep; while there is a depth of at least 2,000 fathoms all across to California on one side, and to Japan on the other. Between the Fiji Islands, New Caledonia, the Solomon Islands, and Australia, the depth is about 1,300 fathoms, and between Sydney and New Zealand 2,600 fathoms; showing, in every case, a general accordance between the depth of sea and the approximation of the several faunas. In a few more years, when it is to be hoped we shall know the contour of the sea-bottom better than that of the continents, we shall be able to arrive at more definite and trustworthy conclusions as to the probable changes of land and sea by which the phenomena of animal distribution in the Pacific have been brought about.

Reptiles of the Polynesian Sub-region.—The researches of Mr. Darwin on Coral Islands, proved, that large areas in the Pacific Ocean have been recently subsiding; but the peculiar forms of life which they present, no less clearly indicate the former existence of some extensive lands. The total absence of Mammalia, however, shows either that these lands never formed part of the Australian or Papuan continents, or if they did, that they have been since subjected to such an amount of subsidence as to exterminate most of their higher terrestrial forms of life. It is a remarkable circumstance, that although Mammalia (except bats) are wanting, there are a considerable number of reptiles ranging over the whole sub-region. Lizards are the most numerous, five families and fourteen genera being represented, as follows:—

1. Cryptoblepharus(Gymnopthalmidæ)Fiji Islands.
2. Ablepharus"All the islands.
3. Lygosoma(Scincidæ)Pelew Islands, New Caledonia.
4. Mabouya"Samoa Islands.
5. Euprepes"Pacific Islands.
6. Dactyloperus(Geckotidæ)Sandwich Islands.
7. Doryura(Geckotidæ)Pacific Islands.
8. Gehyra"Fiji Islands.
9. Amydosaurus"Tahiti.
10. Heteronota"Fiji Islands.
11. Correlophus"New Caledonia.
12. Brachylophus(Iguanidæ)Fiji Islands.
13. Lophura(Agamidæ)Pelew Islands.
14. Chloroscartes"Fiji Islands.