CHAP. III.] 



ZOOLOGICAL EEGIONS. 



47 



and many other remarkable birds. This brief outline being 

 sufficient to show the distinctness and isolation of the Australian 

 region, we will now pass to the consideration of the Western 

 Hemisphere. 



Definition and Characteristic Gimi^ps of the Near die Region. — 

 The Nearctic region comprises all temperate and arctic North 

 America, including Greenland, the only doubt being as to its 

 southern boundary, many northern types penetrating into the 

 tropical zone by means of the highlands and volcanic peaks 

 of Mexico and Guatemala, while a few which are characteristic 

 of the tropics extend northward into Texas and California. 

 There is, however, considerable evidence showing that on the 

 east coast the Rio Grande del Norte, and on the west a point 

 nearly opposite Cape St. Lucas, form the most natural boundary ; 

 but instead of being drawn straight across, the line bends to 

 the south-east as soon as it rises on the flanks of the table- 

 land, forming a deep loop which extends some distance beyond 

 the city of Mexico, and perhaps ought to be continued along 

 the higher ridges of Guatemala. 



The Nearctic region is so similar to the Paige arctic in position 

 and climate, and the two so closely approach each other at 

 Behring Straits, that we cannot wonder at there being a certain 

 amount of similarity between them — a similarity which some 

 naturalists have so far over-estimated as to think that the two 

 regions ought to be united. Let us therefore carefully examine 

 the special zoological features of this region, and see how far it 

 resembles, and how far differs from, the Palsearctic. 



At first sight the mammalia of North America do not seem 

 to differ much from those of Europe or Northern Asia. There 

 are cats, lynxes, wolves and foxes, weasels, bears, elk and 

 deer, voles, beavers, squirrels, marmots, and hares, all very 

 similar to those of the Eastern Hemisphere, and several hardly 

 distinguishable. Even the bison or buffalo " of the prairies, once 

 so abundant and characteristic, is a close ally of the now almost 

 extinct " aurochs " of Lithuania. Here, then, we undoubtedly 

 fjnd a very close resemblance between the two regions, and if 

 this were all, we should have great difficulty in separating them. 

 But along with these, we find another set of mammals, not 



