GEOGRAPHICAL EXTENSION. 259 



2. The Arctic Zone extends from latitude 72° to Beh- 

 ring's Straits, the Arctic Circle in the interior of America, 

 Hudson's Straits, the southern extremity of Greenland, 

 Iceland, and Lapland, and the shores of the White Sea. 



3. The Boreal Zone in America extends southwards to 

 the boundaries of the United States, and in Europe to the 

 Baltic Sea, and latitude 55° in Russia. 



1 4. Temperate Europe is the tract of countries lying be- 

 tween the Baltic and Mediterranean Seas, and extending 

 across Europe from the Pyrenees to the Caucasus. 



5 The Mediterranean Zone includes the countries 

 round that sea and its islands, from the Pyrenees and 

 Black Sea (exclusively) to the N. of Africa, and from 

 Portugal to Asia Minor. 



The United States form a 4th zone in America, nearly 

 corresponding to the temperate and Mediterranean zones 

 in Europe. Only its northern and southern zones are 

 named for each species; the intermediate ones being 

 omitted. 



The columns of figures denote the longitudinal distri- 

 bution of the species ; Europe, Asia, and America being 

 divided each into a Western, Interior, and Eastern Belt, 

 indicated by the figures 1, 2, 3 ; 4, 5, 6 ; 7, 8, 9. Interior 

 Europe embraces Sweden, the West of Russia from the 

 White Sea to the Carpathian Mountains, Germany (except 

 the N. E. angle), Switzerland, the Austrian and Prussian 

 territory, Italy, the islands of the Mediterranean situate be- 

 tween Italy, Spain, and N. Africa, and also the coast of 

 Africa from Tangier to Tripoli. Interior Asia will include 

 the Altaic Mountains, and the interior of Siberia, for some 

 distance on both sides of Lake Baical and the Lena. In- 

 terior America will extend from Hudson's Bay to the 

 Rocky Mountains, and thence northwards to Melville 

 Island, and southwards along the plains of the Mississippi 

 to the Gulf of Mexico. The eastern and western divi- 

 sions will be understood from this explanation of the in- 



