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:—Percidæ (three genera), Acerina, Percarina, Aspro; Comephoridæ (one genus), Comephorus, found only in Lake Baikal; Salmonidæ (three genera), Brachymystax, Luciotrutta, and Plecoglossus; Cyprinodontidæ (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 Palæarctic Vertebrata.—Summarising these details, we find that the Palæarctic 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 Palæarctic 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. Danaidæ; having only a single species in South Europe. 2. Satyridæ; 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. Libytheidæ; a very small family, represented by a single species occurring in South Europe. 5. Nemeobiidæ; a rather small family, also having only one species in Europe, but which constitutes a peculiar genera. 6. Lycænidæ; an extensive family, fairly represented, having about eighty European species; there are two peculiar genera in the Palæarctic region. 7. Pieridæ; rather poorly represented with thirty-two European species; two of the genera are, however, peculiar. 8. Papilionidæ; 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 Palæarctic 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. Hesperidæ; 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 Zygænidæ there are two exclusively European genera, and the extensive genus Zygæna is itself mainly Palæarctic. The small family Stygiidæ has two out of its three genera confined to the Palæarctic region. In the Ægeriidæ the genus Ægeria is mainly Palæarctic. The Sphingidæ have a wider general range, and none of the larger genera are peculiar to any one region.
Coleoptera.—The Palæarctic region is the richest portion of the globe in the great family of Carabidæ, or predacious ground-beetles, about 50 of the genera being confined to it, while many others, including the magnificent genus Carabus, have here their highest development. While several of the smaller genera are confined to the eastern or western sub-regions, most of the larger ones extend over the whole area, and give it an unmistakable aspect; while in passing from east to west or vice-versâ, allied species and genera replace each other with considerable regularity, except in the extreme south-east, where, in China and Japan, some Oriental forms appear, as do a few Ethiopian types in the south-west.
Cicindelidæ, or tiger-beetles, are but poorly represented by about 70 species of the genus Cicindela, and a single Tetracha in South Europe.
Lucanidæ, or stag-beetles, are also poor, there being representatives of 8 genera. One of these, Æsalus (a single species), is peculiar to South Europe, and two others, Cladognathus and Cyclopthalmus, are only represented in Japan, China, and Thibet.
Cetoniidæ, or rose-chafers, are represented by 13 genera, two of which are peculiar to South Europe (Tropinota and Heterocnemis), while Stalagmosoma, ranging from Persia to Nubia, and the fine Dicranocephalus inhabiting North China, Corea, and Nipal, may also be considered to belong to it. The genera Trichius, Gnorimus, and Osmoderma are confined to the two north temperate regions.