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ists that the Palearctic region could not be well characterised by its peculiar genera of birds. In Mr. Sclater's celebrated paper already referred to, he remarks, "It cannot be denied that the ornithology of the Palearctic region is more easily characterised by what it has not than by what it has," and this has been quite recently quoted by Mr. Allen, in his essay on the distribution of North American birds, as if it represented our present know ledge of the subject. But, thanks to the labours of Dr. Jerdon, Mr. Swinhoe, Père David and others, we have now learnt that a large number of birds included in the Indian list, are either mere winter emigrants from Central Asia, or only inhabit the higher ranges of the Himalayas, and thus really belong to the Palearctic region. The result is, that a host of genera are now seen to be either exclusively or characteristically Palearctic, and we have no further difficulty in giving positive ornithological characters to the region. In the tables appended to this chapter, all these truly Palearctic genera will be found printed in italics, with an indication of their distribution, which will sometimes be found more fully given under the respective families in the fourth part of this work. Referring to this table for details we shall here summarise the results.

Of the Sylviidæ or warblers, no less than fourteen genera are either exclusively or characteristically Palearctic, of which Locustella, Sylvia, Curruca and Erithacus are good examples. Of the oriental family Timaliidæ, the genus Pterorhinus is Palæarctic. Of Panuridæ, or reedlings, there are four peculiar genera (comprising almost the whole family); of Certhiidæ, or creepers, one-Tichodroma-which extends southward to the Abyssinian highlands. Of Paridæ, or tits, one-A credula; of Corvidæ, or crows, four-Pica (containing our magpie) being a good example; of Fringillidæ, or finches and buntings, twelve, among which Acanthis, Pyrrhula and Emberiza are good illustrations; of Alaudidæ, or larks, there are two peculiar genera. Leaving the Passeres we next come to peculiar forms among the gallinaceous birds: Syrrhaptes among the Pteroclidæ or sand grouse; four genera of Tetraonidæ or grouse and partridges, and five of Phasianidæ or pheasants, comprising some of the most magnificent birds in the world. Lastly

among the far-wandering aquatic birds we have no less than five genera which are more especially Palæarctic,-Ortygometra, the corn-crake, and Otis, the great bustard, being typical examples. We may add to these, several genera almost confined to this region, such as Garrulus (jays), Fringilla (true finches), Yunx (wrynecks) and some others; so that in proportion to its total generic forms a very large number are found to be peculiar or characteristic.

This view, of the high degree of speciality of the Palearctic region, will no doubt be objected to by some naturalists, on the ground that many of the genera reckoned as exclusively Palearctic are not so, but extend more or less into other regions. It is well, therefore, to consider what principles should guide us in a matter of this kind, especially as we shall have to apply the same rules to each of the other regions. We may remark first, that the limits of the regions themselves are, when not formed by the ocean, somewhat arbitrary, depending on the average distribution of a number of characteristic forms; and that slight local peculiarities of soil, elevation, or climate, may cause the species of one region to penetrate more or less deeply into another. The land boundary between two regions will be, not a defined line but a neutral territory of greater or less width, within which the forms of both regions will intermingle; and this neutral territory itself will merge imperceptibly into both regions. So long therefore as a species or genus does not permanently reside considerably beyond the possible limits of this neutral territory, we should not claim it as an inhabitant of the adjacent region. A consideration of perhaps more importance arises, from the varying extent of the range of a genus, over the area occupied by the region. Some genera are represented by single species existing only in a very limited area; others by numerous species which occupy, entirely or very nearly, the whole extent of the region; and there is every intermediate grade between these extremes. Now, the small localised genera, are always reckoned as among the best examples of types peculiar to a region; while the more wide-spread groups are often denied that character if they extend a little beyond

the supposed regional limits, or send one or two, out of a large number of species, into adjacent regions; yet there is some reason to believe that the latter are really more important as characterising a zoological region than the former. In the case of a single isolated species or genus we have a dying-out group; and we have so many cases of discontinuous species of such groups (of which Urotrichus in Japan and British Columbia, Eupetes in Sumatra and New Guinea are examples), that it is quite as probable as not, that any such isolated species has only become peculiar to the region by the recent extinction of an allied form or forms in some other region. On the other hand, a genus consisting of numerous species ranging over an entire region or the greater part of one, is a dominant group, which has most likely been for some time extending its range, and whose origin dates back to a remote period. The slight extension of such a group beyond the limits of the region to which it mainly belongs, is probably a recent phenomenon, and in that case cannot be held in any degree to detract from its value as one of the peculiar forms of that region.

The most numerous examples of this class, are those birds of the temperate regions which in winter migrate, either wholly or partially, into adjacent warmer countries. This migration most likely began subsequent to the Miocene period, during that gradual refrigeration of the temperate zones which culminated in the glacial epoch, and which still continues in a mitigated form. Most of the genera, and many even of the species of birds which migrate southwards in winter, have therefore, most likely, always been inhabitants of our present Palearctic and Nearctic regions; permanent residents during warm epochs, but only able now to maintain their existence by migration in winter. Such groups belong truly to the temperate zones, and the test of this is the fact of their not having any, or very few, representatives, which are permanent residents in the adjacent tropical regions. When there are such representative species, we do not claim them as peculiar to the Northern regions. Bearing in mind these various considerations, it will be found that we have been very moderate in our estimate of the number of genera VOL. I.-14

that may fairly be considered as exclusively or characteristically Palearctic.

Reptiles and Amphibia.-The Palearctic region possesses, in proportion to its limited reptilian fauna, a full proportion of peculiar types. We have for instance two genera of snakes, Rhinechic and Halys; seven of lizards, Trigonophis, Psammodromus, Hyalosaurus, Scincus, Ophiomorus, Megalochilus, and Phrynocephalus; eight of tailed batrachians, Proteus, Salamandra, Seiranota, Chioglossa, Hynobius, Onychodactylus, Geotriton, and Sieboldia; and eight of tail-less batrachians, Bombinator, Pelobates, Didocus, Alytes, Pelodytes, Discoglossus, Laprissa, and Latonia. The distribution of these and other Palearctic genera will be found in our second vol. chap. xix.

Freshwater Fish.-About twenty genera of freshwater fishes are wholly confined to this region, and constitute a feature which ought not to be overlooked in estimating its claim to the rank of a separate primary division of the earth. They belong to the following families :-Percida (three genera), Acerina, Percarina, Aspro; Comephorida (one genus), Comephorus, found only in Lake Baikal; Salmonidæ (three genera), Brachymystax, Luciotrutta, and Plecoglossus; Cyprinodontidae (one genus), Tellia, found only in Alpine pools on the Atlas Mountains; Cyprinidæ (thirteen genera), Cyprinus, Carassus, Paraphoxinus, Tinca, Achilognathus, Rhodeus, Chondrostoma, Pseudoperilampus, Ochetebius, Aspius, Alburnus, Misgurnus, and Nemachilus.

Summary of Palearctic Vertebrata.-Summarising these details, we find that the Palearctic region possesses thirty-five peculiar genera of mammalia, fifty-seven of birds, nine of reptiles, sixteen of amphibia, and twenty-one of freshwater fishes; or a total of 138 peculiar generic types of vertebrata. Of these, 87 are mammalia and land-birds out of a total of 274 genera of these groups; or rather less than one-third peculiar, a number which will serve usefully to compare with the results obtained in other regions.

In our chapter on Zoological Regions we have already pointed out the main features which distinguish the Palearctic from the Oriental and Ethiopian regions. The details now given will

strengthen our view of their radical distinctness, by showing to how considerable an extent the former is inhabited by peculiar, and often very remarkable generic types.

Insects: Lepidoptera.—The Diurnal Lepidoptera, or butterflies, are not very abundant in species, their number being probably somewhat over 500, and these belong to not more than fifty genera. But no less than fifteen of these genera are wholly confined to the region. Nine of the families are represented, as follows:1. Danaida; having only a single species in South Europe. 2. Satyrida; well represented, there being more than 100 species in Europe, and three peculiar genera. 3. Nymphalidæ; rather poorly represented, Europe having only about sixty species, but there is one peculiar genus. 4. Libytheida; a very small family, represented by a single species occurring in South Europe. 5. Nemeobiidae; a rather small family, also having only one species in Europe, but which constitutes a peculiar genera. 6. Lycaenidae; an extensive family, fairly represented, having about eighty European species; there are two peculiar genera in the Palearctic region. 7. Pierida; rather poorly represented with thirty-two European species; two of the genera are, however, peculiar. 8. Papilionida; very poorly represented in Europe with only twelve species, but there are many more in Siberia and Japan. No less than five of the small number of genera in this family are wholly confined to the region, a fact of much importance, and which to a great extent redeems the character of the Palearctic region as regard this order of insects. Their names are Mesapia, Hypermnestra, Doritis, Sericinus, and Thais; and besides these we have Parnassius— the "Apollo" butterflies-highly characteristic, and only found elsewhere in the mountains of the Nearctic region. 9. Hesperida; poorly represented with about thirty European species, and one peculiar genus.

Four families of Sphingina occur in the Palæarctic region, and there are several peculiar genera.

In the Zyganida there are two exclusively European genera, and the extensive genus Zygana is itself mainly Palearctic. The small family Stygiidae has two out of its three genera

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