Page:EB1911 - Volume 28.djvu/1033

Rh peculiar avian families include the birds-of-paradise (Paradiseidae), the honeysuckers (Meliphagidae), and the lyre-birds (Menuridae) among the perching group, the cockatoos (Cacatuidae) and lories (Loriidae) among the parrots, the mound-builders, or brush-turkeys (Megapodiidae) among the game-birds, and the cassowaries and emeus (Casuariidae and Dromaeidae) in the ostrich group. The peculiarity of the region is also marked by the absence of certain widely spread family groups, such as the barbels (Megalaemidae), the otherwise cosmopolitan woodpeckers (Picidae), the trogons (Trogonidae), and the pheasant and partridge tribe (Phasianidae).

The reptiles, owing probably to tneir earlier radiation, are much less peculiar, such widely spread types as the monitors (Varanidae) and skinks, (Scincidae) being abundant, as are also crocodiles (Crocodilidae). The tortoises belong, however, exclusively to the side-necked group (Pleurodira), now restricted to the southern hemisphere; among these the most noteworthy being the giant horned tortoise (Mioiania) from the Pleistocene of Queensland, which belongs to a genus elsewhere known only from the South American Tertiary. The Australian lung-fish (Ceratodus, or Neoceratodus) is the sole survivor of a widely spread Triassic and Jurassic type. The salmon tribe (Salmonidae), however, is notable for its absence, although one peculiar form occurs in New Zealand; and the Cyprinidae, or carps, are wanting throughout 'the realm, this absence extending to Celebes, although in Borneo the group is abundantly represented.

New Zealand, here provisionally included in a separate Polynesian region, is characterized by the absence of all indigenous mammals except two bats, each representing a peculiar genus. Among birds, the Neogaeic family Meliphagidae includes several peculiar genera, as does also the widely spread starling group (Sturnidae) ; while the parrots of the genera Siringops and Nestor are likewise peculiar. Still more noteworthy is the abundance of the ostrich group, represented by the living kiwis (Apteryx), and the moas (Dinornithidae) which have been exterminated within comparatively recent times. Reptiles are scarce, but among them the tuatera lizard (Sphenodon) is especially noteworthy on account of being the sole survivor of an ordinal group (Rhynchocephalia) widely spread during Triassic and Jurassic times.

Of the Hawaiian area (whether or no rightly regarded as a distinct region), it must suffice to state that it is the sole habitat of the gorgeously coloured birds known as mamos, or sickle-bills (Drepanididae).

With regard to the origin of the modern fauna of Notogaea, and more especially the Australian region, as here restricted, we enter extremely debatable ground. Dr Wallace, who refused to admit the existence of any great inter-continental connexions in the past, was of opinion that Australia received the ancestors of its marsupials and monotremes from Asia by way of the Austro-Malayan area (as it certainly has its rodents) "far back in the Secondary period." This view has been endorsed by the present writer who suggested the early Eocene as the most probable date of immigration; and it has also received the assent of Dr Max Weber, who is of opinion that in pre-Tertiary—very likely Cretaceous—times Australia was united by land with Asia. A Euro-Asiatic fauna inhabited this land, from which during the Eocene a southern portion was cut off by partial submergence, this southern portion being the modern Australia and New Guinea, the home of monotremes, marsupials and ancient forms of other groups, such as cassowaries and birds-of-paradise, while widely distributed specialized types are wanting. Northwards extended a coral-sea, in the islands of which dwelt primitive rodents, insectivores and other ancient groups, with perhaps cuscuses. During the Miocene, great changes of level took place in the archipelago, which attained its present form in the Pleistocene. Celebes was insulated early, Java later. Intermittent land-connexions took place, which allowed of periodical immigrations of Asiatic forms from one side and of Australian types from the other. The question is left undecided whether the cuscuses of the Austro-Malayan islands are remnants of the primitive Euro-Asiatic fauna or later immigrants from Australia. The suggestion is also made that the Australian and Philippine rodents are survivors of the original pre-Tertiary fauna, although it is admitted that the specialization of Hydromys is against this. The author fails to see [any evidence in favour of a former connexion of Australasia with either South America or a former large antarctic continent (Antarctica).

While admitting that this may be the true explanation, Mr B. A. Bensley considers it possible that opossums (Didelphyidae), which he regards as the ancestral stock of the marsupials, may have effected an entrance into Neogaea by way of Antarctica. In either event, he would place the date of entry as post-Eocene; but against this view is the occurrence of remains of a diprotodont marsupial (Wynyardia) in Tasmanian strata believed to be of Eocene age. Prof. Baldwin Spencer is also of opinion that the

Australian marsupials and monotremes reached their present habitat by means of a land-connexion in the south subsequent to the insulation of New Zealand. This, of course, implies the existence of an extinct southern marsupial fauna of which we have no knowledge except in the case of the Epanorthidae of Patagonia.

That Australia formed part of a great equatorial land-belt connecting the southern continents in Jurassic times appears to be demonstrated by the evidence of the "Gondwana flora." The question is whether such a connexion—either by way of Antarctica or not—persisted in the case of Neogaea long enough to admit of the ancestors of the modern fauna (supposing it all to have come by a southern route) having effected an entrance. The existence of such a land-bridge was suggested by Sir Joseph Hooker in 1847; and the idea of a late connexion between Neogaea and Notogaea has been adopted by L. Riitimeyer (1867), Captain F. W. Hutton (1873), Prof. H. O. Forbes (1803), Mr C. Hedley (1895), Dr H. von Ihering (1891 and 1900), Prof. H. F. Osborn, who takes an intermediate view of the extent of the part played by Antarctica (1900), and by Dr A. F. Ortmann (1902). On the other hand, Dr T. Gill (1875) believed in the existence of an "Epgaea" connecting the three great continents exclusive of Antarctica; and in 1884 Capt. Hutton, abandoning his former view, suggested the connexion of Australia and South America by means of a mid-Pacific continent. A summary of these views, with references, is given by Dr Ortmann in vol. xxxv. pp. 139-142 of the American Naturalist (1901).

So far as mammals are concerned, the evidence in favour of a comparatively late land-connexion is weakened by the recent view that certain supposed Patagonian Tertiary marsupials, such as Prothylacinus, are really creodont Carnivora. On the other hand (putting aside these carnivores), Mr W. J. Sinclair is of opinion that the living South American marsupial Caenolestes and its extinct relatives are annectant forms between diprotodonts and polyprotpdonts, and not far removed from the ancestral stock which gave rise to the Australian phalangers. The occurrence in the Tertiary of Patagonia of primitive opossums, which cannot be regarded as ancestral to the modern South American forms, is also an important determination. From this, coupled with the testimony afforded by the invertebrate faunas, he considers himself justified in stating that "considerable evidence is now available to show that a land-connexion between Patagonia and the Australian region existed not later than the close of the Cretaceous or the beginning of the Tertiary, and it is possible that at this time the interchange of marsupials between the two continents was effected. Whether the marsupials originated in South America and migrated thence to Australia, or the reverse, cannot at present be determined." The above-mentioned tortoises of the genus Miolania also appear to afford strong evidence of the persistence of the Jurassic connexion between Notogaea and Neogaea to a comparatively late epoch.

Again, Prof. W. B. Benham, from the evidence of earthworms, is strongly disposed to believe in a late connexion between the areas in question. From their invariable association with angiospermous plants, this author is of opinion that earthworms are a comparatively modern group, which did not attain any important development before the Cretaceous. The ancestral type would appear to have been more or less nearly related to the existing Notiodrilus, of which the headquarters, if not the birthplace, was the "Melanesian plateau." New Zealand and the neighbouring islands, which possess the most ancient worm-fauna, were separated at an early date from this plateau. From this area the primitive worms travelled in one direction into the Austro-Malayan countries, while in another, by way of Antarctica, they reached South America and Africa. With this brief summary of the chief views, this part of the subject must be dismissed without the writer being committed to any definite conclusion.

Next to Notogaea the most distinct faunistic continental area, so far at any rate as its present and later Tertiary mammals are concerned, is Neogaea, containing, as we have seen, only Neogaea. the Neotropical region. It is remarkable as being, with the exception of Notogaea, the only land-area which contains at the present day more than one living genus of marsupials, and also a large middle Tertiary marsupial fauna. The living marsupials include a large number of true opossums, constituting the family Didelphyidae and Caenolestes the surviving representative of the Epanorthidae of the Patagonian Tertiaries. The opossums are represented by the genera Chironectes and Didelphys; the latter divisible into a number of sub-genera of which the typical group alone ranged into North America. Whether the modern opossums belong to the endemic Neogaeic fauna, or whether they are late immigrants from the north (where they were represented in the Oligocene of both hemispheres), is a question in regard to which a definite answer can scarcely at present be given. It appears, however, that Microbiotherium and certain allied forms from the middle Tertiary of Patagonia are endemic representatives of the Didelphyidae which did not give rise to the modern types. The Epanorthidae, in the opinion of Prof. Max Weber, indicate a subordinal group by themselves; and if this be correct their evidence