mous; Opisthocomida, the hoazin; Thinocorida; Cariamidæ : Aramidæ ; Psophiida, or trumpeters; Eurypygidæ, or sun-bitterns; and Palamedeidæ, or horned screamers. The Trochilidæ, or humming-birds, are especially noteworthy on account of their great numbers. Six families of reptiles have also been claimed as peculiar to the realm, and among the lizards the family of Iguanidæ is remarkably developed. Four families of amphibians and four of fishes are also considered as restricted to the realm. The relation between the fishes of South America and Africa is another feature of special significance: there are three families shared between the two, and found nowhere else, and genera of the respective families are not distantly related, although none are actually common to the two realms.

VI. THE AMPHIGEAN REALM.

The Temperate South American Realm may retain provisionally. the limits assigned to it by Mr. Allen, and as these have already been specified when considering Mr. Allen's views, it is unnecessary to repeat them here. Within its limits occur representatives of several peculiar groups; there are 18 families of terrestrial mammals, two of which (the Chinchillida and Chlamyphorida) are almost confined to it, and two (Urside and Camelida) are shared with the northern realms without occurring in the contiguous realm; 42 socalled families of birds, three of which (the Chionididæ, Thinocorida, and Rheida) scarcely or not at all encroach northwards; 15 families of reptiles; 11 families of amphibians; 5 families of fishes, two of which are shared with New Zealand and Tasmania, and scarcely extend into Tropical America; and one family of Myzonts, also shared with New Zealand and Tasmania.

VII. THE AUSTROGAN REALM.

The Australian Realm is of all the most distinctly defined by its fauna. As it will be here limited, it comprises Australia and the immediately outlying islands, and the Austro-Malayan Archi

pelago. It is limited northward by Wallace's line or strait, which separates Lombok from Bali and Celebes from Borneo, including Papua or New Guinea and the Solomon Islands, to the eastward, and southward embraces Tasmania or Van Diemen's Land. It is especially distinguished by its numerous marsupial mammals, and by the almost complete restriction of the class to representatives of that order, the rodents and the bats; the Monotremes are also characteristic of the realm, and entirely confined to it. The class of birds likewise has a number of very characteristic types: chief of these are Megapodidæ and Casuaridæ, but there are several others—e. g., the Paradiseidæ, Meliphagidæ, Menuridæ, and Atrichida-that are almost equally peculiar. The reptiles and amphibians are perhaps less noteworthy, although they present some interesting features of detail. The fresh-water fishes are, however, especially remarkable; while many of what may be called marine families are represented by fluviatile species, there are several that are peculiar to it or only found elsewhere in South America. Among the former is the family Ceratodontidæ, which in former geological epochs was extensively represented in other parts of the world, but is now peculiar to Australia. Among the latter are the families Percophidide, Haplochitonidæ, Galaxiida, Osteoglosside, and Symbranchide. The articulates and mollusks also afford a large number of characteristic forms. The primary subdivisions of the realm are two.

VIII. THE ORNITHOGÆAN REALM.

The New Zealand sub-region of Mr. Wallace cannot be satisfactorily referred to the Australian or any other realm, and, although its peculiar characters are not very salient, it should apparently be isolated as a peculiar realm. The name Ornithogæa, proposed nearly ten years ago, may be retained for it. In prehistoric times, it was the abode of a number of gigantic struthiiform birds, which have been referred to one or two peculiar families-the Dinornithida and Palapterygidæ―and a related family-the Apterygidæ―is still

represented by four species. There are also many other birds representing genera peculiar to New Zealand. Here also live the only survivors (Sphenodon or Hatteria) of an order of reptiles (Rhynchocephalia) which, in ancient times, had a wide distribution. The fresh-water fishes are few, but noteworthy. One genus (Galaxias) is common to the temperate portions of Australia and South America, another (Prototroctes) to New Zealand and South Australia, a third (Neochanna) of the family of Galaxiidæ is peculiar, and also peculiar is a genus (Retropinna) distantly related apparently to the Argentines (smelts, etc.) of the northern realms. The Gastropod mollusks, and other invertebrates exhibit a peculiar association of types, which, at the same time, re-enforces the distinctness of the realm and gives rise to special problems of zoogeography.

IX. THE NESOGÆAN REALM.

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The restricted Polynesian realm is distinguished by negative rather than positive characters, and is to some extent a refuge of the destitute." It includes all the islands of the tropical portions of the Pacific Ocean combined under the general name Polynesia. It is distinguished from all others by the total-or almost totalabsence of indigenous types of mammals. The other common characters are very few; the avian types, on the whole, recall mostly the Australian forms. There are, according to Wallace, "not more than about 50 genera and about 150 species of landbirds." It is possible that these islands are the remains of one or more continental areas, and that at least most of them have been submerged and lost their mammals, and on emergence, or rather upheaval, have been peopled from other territories. The analysis of this group would detain us too long, and this realm may, for the present, be considered as a provisional one, to be hereafter studied and properly limited.

All the primary zoogeographical divisions recognized by Messrs. Wallace and Allen have now been considered, but the relations of the several realms to one another may be glanced at with profit. As

will be remembered, there are fundamental differences involved in this respect between the views of Messrs. Wallace and Allen. Mr. Wallace's sequence of his "regions" implies a reminiscence of an ancient idea, which was expressed in the translation of the terms "Old World" and "New World" into respectively "Palæogæa" and "Neogæa" The realms of Mr. Allen traverse such primary groups, and are rather subordinated to climatic considerations. Still other groupings have been proposed, as, for example, by Professor Huxley, who has segregated the Eurasiatic, Indian, and African realms into an "Arctæoga," and the South American, or AustroColumbian, Australasian, and New Zealand ones into a "Notogæa." And the present author has proposed to contrast the North American, Eurasiatic, and Indian realms under the denomination Cenoga, with an Eogaa, comprising the African, South American, Australian, and New Zealand realms. Let us look at some of the facts which may determine our opinion in the case.

On the one hand, those forms of animal life which are capable of easy extension over extensive bodies of land or water, such as the birds, which represent the highest types, physiologically speaking, of life, are distributed in a manner to a large extent co-ordinate with the present arrangement of land and water. The birds seem to have especially become modified and adapted to the present topographical features of our earth at a (geologically speaking) recent epoch. On the other hand, those animals of a more lethargic character, or which are prevented by physical environments from extending their range, are grouped entirely otherwise. This is especially the case with the fresh-water animals of various kinds, and notably with the fresh-water fishes.

If the inhabitants of the fresh waters of the globe are taken into consideration, the several realms we have defined may be combined in quite a curious manner, which entirely contradicts the relations which the present combinations of land and water would suggest. It will then be seen that the inhabitants of the northern portions of the several continents of North America, Europe, and Asia belong,

in a great degree, to the same types; and although the realms thus associated are characterized by a number of forms peculiar severally to each of them, they form a natural whole in contradistinction to the others. Very closely connected with this division is the East Indian, and this forms with them an integral portion of a great super-realm or hemisphere.

In striking contrast with the association of forms characteristic of the several divisions alluded to are the fresh-water types of Australia. Most closely related to Australia in this respect is South America, and in the fresh waters of that continent are to be found several types which are common to the two continents. The only remaining continent-Africa—although presenting some forms that are common to it and India, on the whole furnishes us with an association of fresh-water forms which recalls the South American realm more than it does any other. Several families of fishes and a number of types of other animals are common to the two and are found nowhere else.

Combining these facts into a systematic whole, it has been proposed to segregate the several realms in the manner hinted at, and to combine under the name Eogia (1) the Australian, (2) South American, and (3) African realms; and under the name Cenoga (4) the North American, (5) the European, and (6) the East Indian realms. Eogaa gives to us a number of forms which remind us of the ancient inhabitants of the northern hemisphere, and hence the name, while Cenoga has lost most of the forms that were characteristic of the past, and presents the newest aspect of the earth-faunas in contradistinction with the other.

An explanation of these relations may be found in one or other of two hypotheses. (1) The like forms may have originated where they are now found, and have been ever confined within proximately their present limits; or (2) they may be the survivors of anciently widely-distributed races. Neither hypothesis of itself is a sufficient explanation of all the associations in question, but each is applicable to different cases