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 Region ” 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 lands. 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 Palearctic 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 Rangifer. Two species of widely 
dispersed genera are also exclusively arctic, Ursus maritimus 
and Vulpes 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 Uriide, 
Uria, Catarractes, and Mergulus; and the small family Alcide, 
consisting of the genera Alca and Fratercula. Our total then 
. 1s, 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 tv the two northern regions, or we 
