350 AN ELEMENTARY TEXT-BOOK OF BIOLOGY. 



fresh-water, N. America to Mexico and Cuba. Ganoid fishes 

 are of great geological antiquity, and were formerly a widely 

 spread marine group. Most of the forms now surviving have 

 gradually accommodated themselves to a life in rivers, lakes, &c., 

 where the struggle for existence is less severe. 



The peculiar distribution of the Dipnoi (p. 153) can be explained 

 similarly. 



The Marsupialia and Edentata (p. 354) are also good examples 

 of interrupted areas of distribution. 



Zoological Regions, characterized by the presence of peculiar 

 families and genera, and by the absence of other families and 

 genera, have been formed for sea and land. The most useful 

 division of the latter is chiefly based on the Mammalia, but 

 applies very well to birds and reptiles and fairly to other groups. 

 The regions thus established are six in number. 



I. Palcearctic Region. Temperate Europe and Asia and N. 

 temperate Africa. Extends "W. to Iceland, the Azores, and 

 Cape Verde Islands, and E. to Behring Straits and Japan. 

 Southern boundary somewhat indefinite, tropic of Cancer in 

 Africa and Arabia, river Indus, Himalayas, Nanling mountains. 



II. Ethiopian Region. Africa and Arabia south of the tropic 

 of Cancer, and including Madagascar. 



III. Oriental Region. Asia, S. of Region I., and the western 

 part of the E. Indies. The eastern boundary of this region 

 {Wallaces line] passes between Bali, Borneo, and the Philippines 

 on the one hand, Lombok and Celebes on the other. The 

 former islands are therefore in the Oriental Region, the latter in 

 the Australian Region. 



IV. Australian Region. Australia, New Guinea, New Zealand, 

 with the smaller islands from Wallace's line to the Marquesas and 

 Low Archipelago, and the tropic of Cancer to the Macquarie 

 Islands. 



V. Neotropical Region. S. America, the W. Indies, and tropical 

 N. America, with the exception of the central part of the Mexican 

 table-land. 



VI. Neardic Region. Arctic and temperate N. America, with 

 the central part of the Mexican table-land. 



