DISTRIBUTION OF THE FAUNAS. 167 



425. Some of the herbivorous Mammals, the Bats, and 

 the reptiles which feed on insects, pass the winter in a state 

 of torpor, from which they awake in spring. Others retire 

 into dens, and live on the provisions they have stored up 

 during the warm season. The Carnivora, the Ruminants, 

 and the most active portion of the Rodents, are the only 

 animals that do not change either their abode or their 

 habits. The fauna of the temperate zone thus presents an 

 ever-changing picture, which may be considered as one of 

 its most important features, since these changes recur with 

 equal constancy in the Old and the New World. 



426. Taking the contrast of the vegetation, as a basis, 

 and the consequent changes of habit imposed upon the 

 denizens of the forests, the temperate fauna has been 

 divided into two regions ; a northern one, where the 

 trees, except the pines, drop their leaves in winter, and 

 a southern one, where they are evergreen. Now, as 

 the limit of the former, that of the deciduous trees, coin- 

 cides, in general, with the limit of the pines, it may be 

 said that the cold region of the temperate fauna extends as 

 far as the pines. In the United States this coincidence is 

 not so marked as in other regions, inasmuch as the pines 

 extend into Florida, while they do not prevail in the West- 

 ern States ; but we may reckon as belonging to the southern 

 portion of the temperate region, that part of the country south 

 of the latitude where the Palmetto or Cabbage-tree (Cha- 

 mczrops) commences, namely, all the States to the south of 

 North Carolina ; while the States to the north of this limit 

 belong to the northern portion of the temperate region. 



427. This division into two zones is supported by obser- 

 vations made on the maritime faunas of the Atlantic coast. 

 The line of separation between them, however, being influ- 

 enced by the Gulf Stream, is considerably farther to the 

 north; namely, at Cape Cod. It has been ascertained 

 that of one hundred and ninety-seven Mollusks inhabiting the 



