1868.] PROF. HUXLEY ON THE ALECTOROMORPHjE. 317 



rated portions of the south world, and justify the adoption for it 

 of the title oi Notogcea, in contrast to the north world, or Arctogeea. 



The eastern boundary between Arctogsea 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- 

 givorous Bats and viverrine Curnivora — 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 

 Mam.mals or Birds which is not to be met with in the great provinces 

 which it separates. Negatively, however, it is extremely remark- 

 able*; why Borneo and the Philippines should have, at once, so much 

 and so little in common with Asia, New 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 an area of the 

 North-American continent, which extends from the Pacific to the 

 Atlantic, and has no definite boundaries — southern forms and north- 

 ern 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 pro- 

 vinces, 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 groiqis. 



If we consider Arctogsea 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 Aus- 

 tralia over a very wide extent of Arctogsea, while they are wholly 

 wanting in Austro-Columbia : — 



Hemij^odidce, Gruidce, 



Otididx, Meropidce, 



GlareolidcB, Coracida, 



among Birds ; and the Frugivorous Bats among Mammalia. 



* See Mr. Wallace's remarks on the fauna of these islands, P. Z. S. 1SG4, p. 277. 

 t See ' The Greographical Distribution of Mammals,' p. 8.3. 



