OCR Text |
Show 1868.] PROF. HUXLEY ON THE ALECTOROMORPHAE. 317 rated portions of the south world, and justify the adoption for it of the title of Notogcea, in contrast to the north world, or Arctogeea. The eastern boundary between Arctogaea and Australasia is formed, not by a line, but by a broad zone of border islands, extending between Asia and Australia from the Philippines, or even Formosa, to Madagascar. As a distributional area, it is characterized by Le-murini or Catarrhini, or both-by large Insectivores where there are no Marsupials, or small Insectivores where there are-by fru- !>ivorous Bats and viverrine Carnivora-and by the paucity of other Mammalia. It does not appear that there is anything independent about this fauna. So far as I know, it presents no considerable group of either Mammals or Birds which is not to be met with in the great provinces which it separates. Negatively, however, it is extremely remarkable*; why Borneo and the Philippines should have, at once, so much and so little in common with Asia, N e w Guinea with Australia, Madagascar with Africa, are problems not easy of solution, though Mr. Murray's ingenious suggestions as to the possible influence of partial submersion appear to me to be worthy of much attention *f. The western frontier of Arctogaea is formed by au area of the North-American continent, which extends from the Pacific to the Atlantic, and has no definite boundaries-southern forms and northern forms overlapping, more or less, from the isthmus to the lakes. If this portion of North America were now to be partially submerged and broken up into islands, Mexico would stand in the same relation to Austro-Columbia as Sumatra does to India ; and the population of the country north of the lakes would resemble that of Northern Asia more than the fauna of New Guinea does that of Australia. The intermediate islands would correspond with the chain of the Indian archipelago. It is a trite remark that none of the great zoogeographical provinces, however we may circumscribe them, are sharply defined from one another, if the larger groups, such as genera and families, are taken into consideration. Each province has its characteristic groups limited to itself; but every two are also united by annectent groups. If we consider Arctogaea as having Austro-Columbia on the west, and Australasia on the east, these annectent groups will be divisible into eastern and western. Now it is a remarkable circumstance that a large proportion of these annectent groups, whether eastern or western, are restricted to the two provinces which they connect, and do not extend into the third. Thus the following eastern annectent groups extend from Australia over a very wide extent of Arctogaea, while they are wholly wanting in Austro-Columbia:- Hemipodidee, Gruidee, Otididce, Meropidee, Glareolidce, Coracidee, among Birds ; and the Frugivorous Bats among Mammalia. * See Mr. Wallace's remarks on the fauna of these islands, P. Z. S. 1864, p. 277. t See ' The Geographical Distribution of Mammals,' p. 83. |