DISTRIBUTION IN SPACE 113 



over the tropic seas right round the world, but 

 one of them is apparently much more local 

 than the other, confined to the Eastern seas. 



The Anseriformes constitute collectively an- 

 other absolutely cosmopolitan order, but two 

 of the sub-orders have a distribution considerably 

 more restricted. These latter are the Screamers, 

 which are confined to the Neotropical Region, 

 and the Flamingoes occupy the tropical por- 

 tions of Asia (with South Europe), Africa, and 

 America, but are absent from Australia. The 

 birds composing the sub-order Anseres are the 

 great cosmopolites. The distribution of the 

 various sub-families into which the Anatidae is 

 divided is as follows. The Swans are some- 

 what remarkable in their dispersal, because their 

 area of distribution is a discontinuous one. 

 Swans are distributed over the arctic and tem- 

 perate portions of the Palaearctic and Nearctic 

 Regions and the more southern parts of the 

 Neotropical Region, whilst the Black Swan is 

 exclusively Australian. Geese, of which several 

 sub-families are recognised, are practically cos- 

 mopolitan. The more typical Geese are all 

 Northern Hemisphere species, some of which 

 are specially arctic in their distribution. Ducks 



may be classed as absolutely cosmopolitan, but 



H 



