chap, iv.] ZOOLOGICAL REGIONS. 69 



The proposal to consider the Arctic regions as constituting one of 

 the primary zoological divisions of the globe, has been advocated 

 by many naturalists. Professor Huxley seems to consider it 

 advisable, and Mr. Allen unhesitatingly adopts it, as well as an 

 " antarctic " region to balance it in the southern hemisphere. 

 The reason why an " Arctic Eegion " finds no place in this work 

 may therefore be here stated. 



No species or group of animals can properly be classed as 

 " arctic," which does not exclusively inhabit or greatly prepon- 

 derate in arctic lauds. For the purpose of establishing the 

 need of an " arctic " zoological region, we should consider chiefly 

 such groups as are circumpolar as well as arctic ; because, if 

 they are confined to, or greatly preponderate in, either the 

 eastern or western hemispheres, they can be at once allocated to 

 the Nearctic or Palasarctic regions, and can therefore afford no 

 justification for establishing a new primary division of the 

 globe. 



Thus restricted, only three genera of land mammalia are truly 

 arctic : Gulo, Myodes, and Rangifcr. Two species of widely 

 dispersed genera are also exclusively arctic, Ursits maritimus 

 and Vilifies lagopus. 



Exclusively arctic birds are not much more numerous. Of 

 land birds there are only three genera (each consisting of but a 

 single species), Pinicola, Nyctea, and Surnia. Lagopus is cir- 

 cumpolar, but the genus has too wide an extension in the 

 temperate zone to be considered arctic. Among aquatic birds 

 we have the genus of ducks, Somateria ; three genera of Uriidse, 

 Uria, Catarractes, and Mergulus ; and the small family Alcidse r 

 consisting of the genera Alca and Fratercula. Our total then 

 is, three genera of mammalia, three of land, and six of aquatic 

 birds, including one peculiar family. 



In the southern hemisphere there is only the single genus 

 Aptenodytes that can be classed as antarctic ; and even that is 

 more properly south temperate. 



In dealing with this arctic fauna we have two courses open 

 to us ; we must either group them with the other species and 

 genera which are common to the two northern regions, or we 



