chap, xni.] THE AUSTRALIAN REGION. 461 



and Steamer Duck) are probably cases of abortion of use- 

 less organs, and that the common ancestors of the various 

 forms of Struthiones may have been capable of a moderate 

 degree of flight ; or they may have originated in the northern 

 hemisphere, as already explained in Chap. XI. p. 287. The exis- 

 tence of two, if not three, distinct families of these birds in New 

 Zealand, proves that the original type was here isolated at a 

 very early date, and being wholly free from the competition of 

 mammalia, became more differentiated than elsewhere. The 

 Hatteria is probably coeval with these early forms, and is the 

 only relic of a whole order of reptiles, which once perhaps 

 ranged far over the globe. 



Still less does any other form of animal inhabiting New Zea- 

 land, require a land connection with distant countries to account 

 for its presence. With the example before us of the Bermudas 

 and Azores, to which a great variety of birds fly annually over vast 

 distances, and even of the recent arrival of new birds in New 

 Zealand and Chatham Island, we may be sure that the ancestors 

 of every New Zealand bird could easily have reached its shores 

 during the countless ages which elapsed while the Dinornis and 

 Apteryx were developing. The wonderful range of some of the 

 existing species of lizards and fresh-water fish, as already given, 

 proves that they too possess means of dispersal which have 

 sufficed to spread them, within a comparatively recent period, 

 over countries separated by thousands of miles of ocean; and the 

 fact that a group like the snakes, so widely distributed and for 

 which the climate of New Zealand is so well adapted, does not 

 exist there, is an additional proof that land connection had nothing 

 to do with the introduction of the existing fauna. We have 

 already (p. 398), discussed in some detail the various modes in 

 which the dispersal of animals in the southern hemisphere has 

 been effected ; and in accordance with the principles there estab- 

 lished, we conclude, that the New Zealand fauna, living and 

 extinct, demonstrates the existence of an extensive tract of land 

 in the vicinity of Australia, Polynesia, and the Antarctic con- 

 tinent, without having been once actually connected with either 

 of these countries, since the period when mammalia had peopled 



