332 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



shared by the contiguous region to the southward. For the present I 

 lirefer to still retain it as a division of the first rank. It is character- 

 ized mainly by the paucity of its life, as compared with every region 

 except the Antarctic, and by what it has not rather than by the posses- 

 sion of peculiar species or groups. It wholly lacks both Amphibian and 

 Beptilian life, is almost exclusively the summer home of many birds, 

 and forms the habitat of the Esquimaux, the Arctic Fox, the Polar Bear, 

 the Musk Ox, the Polar Hare, the Lemmings, the Walruses, the T^arwhal, 

 and the White Whale, which are confined within it. It has no Chiroptera 

 nor Insectivora, two or three species of Shrews, however, barely reaching 

 its southern border. It shares with the cold-temperate belt the presence 

 of the Moose and the Eeindeer, several Pinnipeds, a number of boreal 

 species of GUres, several fur-bearing Camivora., and a considera.ble num- 

 ber of birds. Its southern boundary may be considered as coinciding 

 very nearly with the northern limit of arboreal vegetation, and hence 

 approximately with the isotherm of 32° P. Its more characteristic 

 terrestrial forms range throughout its extent, none being restricted 

 to either the North American or Europseo- Asiatic continent. Hence it 

 is indivisible into regions of the second and third grades (regions and 

 provinces), and may be considered as embracing a single hyperborean 

 assemblage of life. 



II. — NOETH-TEMPERATE REALM. 



Very few writers on zoological geography have failed to recognize 

 the striking resemblance the fauna of Temperate Korth America bears 

 to that of the corresponding portion of the Old World. The resem- 

 blance is less in the Avian class than among mammals, but is generally 

 acknowledged as obtaining even there. Dr. Sclater, while admitting 

 a strong resemblance between these areas, considered them as separable 

 into two primary regions, in which view of the case he has been followed, 

 among prominent writers on the subject, by Dr. Giinther, Mr. Wallace, 

 Mr. Murray, and Professor Ccpe. Dr. Giinther, while provisionally 

 accepting Dr. Sclater's "Nearctic" and "Palaiarctic" regions, refers 

 I)ointedly to the disagreement of the distribution of Batrachians with 

 these divisions ; for in discussing the distribution of this class he says, — 

 " Dissimilarity and similarity of the Batracho-fauna depend upon zones. 

 Palsearctic and Nearctic regions resemble each other more than any other 

 third; the same is the case with Australia and South America; the 

 Ethiopian region exhibits similarity with South America, as well as 

 with the East Indies, but more especially with the latter."* Mr. Murray 

 admits that " the boreal extremity of North America is tinged with a 

 Europeo-Asiatic admixture", which he regards as "an extraneous ele- 

 ment grafted upon the genuine stock, and easily eliminated from it ".f 

 But in his map of "Great Mammalian Regions " the boreal parts of 



* Proc. Zool. Soe. Lond., 1858, p. 390. 

 tGeogr. Dist. Mam., p. 312. 



