284 



REGIONS OF DISTRIBUTION 



eating the facts of geographical distribution, into six regions — 

 the Palaearctic, Oriental, Australasian, Ethiopian, Nearctic, and 

 Neotropical. To these is sometimes added a seventh, the Neant- 

 arctic, consisting of Chili and Patagonia (and certain islands of 

 the south Atlantic) ; but since the MoUusca of Chili unmistak- 

 ably form a part of the Neotropical fauna, it seems hardly worth 

 while to recognise a separate region for those of the extreme 

 south of South America, which have no peculiar characteristics. 



In certain points the exact limits of these regions, as in- 

 dicated by the MoUusca, will probably not correspond to those 

 which are marked out by other zoological classes. Wallace's line, 

 for instance, does not exist, as far as the MoUusca are concerned. 



These regions mS,y he further subdivided into sub-regions, 

 thus : — 



Palaearctic 



Oriental 



Sub-regions 

 I Septentrional 



■ Mediterranean 

 ( Central Asiatic 

 I Indo-Malay 



) Chinese 



Regions 



Sub-regions 

 Central African 



Nearctic 



j Papuan 

 Australasian ■; Australian 

 ( Polynesian 



1 Uei 

 Ethiopian -^ South African 

 ( Malagasy 

 f American 

 I Califoriiian 

 f Antillean 

 Central American 

 Neotropical - Colombian 

 Brazilian 

 Chilian 



A. The Palaearctic Region 



The southern boundary of this region is the northern limit of 

 the African Sahara, the Mediterranean forming no break what- 

 ever in its continuity. In Asia this boundary is less well 

 marked, but roughly corresponds to the southernmost of the vast 

 ranges of mountains which border the great tablelands of central 

 Asia. Across Africa the line of desert is well defined ; but in 

 the north-east, as the desert approaches more nearly to the sea, 

 the African extent of the region is correspondingly narrowed 

 until it becomes little more than a strip of coast land, scarcely 

 widening even in Lower Egypt. On the Morocco coast, 

 Palaearctic land forms penetrate as far south as Cape Nun.^ 

 At its eastern extremity the line becomes less well defined, but 



1 Morelet, Journal de Conch. 1875, p. 194. 



