i 4 INDEX FAUNAE NOV& ZEALANDI&. 



many groups of animals, and must have remained isolated ever 

 since. 



Professor Gill, writing about the fishes, says that ' the number 

 of species apparently peculiar to the province, and, therefore, 

 modified from other or earlier representatives, indicates a long 

 period of isolation in accordance with its distance from the nearest 

 continents and the depth of the intervening ocean.' He thinks it 

 probable ' that there existed some terrestrial passage-way between 

 the several [Antarctic] regions at a time as late as the close of the 

 Mesozoic. The separation of the several areas must, however, 

 have occurred little later than the earlier Tertiary, inasmuch as the 

 salt-water fishes of corresponding isotherms found along the 

 coasts of the now widely-separated lands are to such a large 

 extent specifically different.' ' In general,' he says, ' change 

 seems to take place more rapidly among marine animals than 

 fresh-water representatives of the same class.' And thus he 

 explains the closer relations in Galaxias and Geotria than in the 

 marine fishes. 



Mr. H A. Pilsbry thinks that the Epiphalhgonous land-snails 

 invaded New Guinea from the north before the Eocene period, 

 and yet they were unable to reach New Zealand. 



It must be remembered that the flora of New Zealand shows 

 the same elements as the fauna, and. as the Antarctic plants are 

 far more numerous than the undoubted Antarctic land animals, 

 I tried a good many years ago to use them as a means of ascer- 

 taining whether the migration from the north occurred before or 

 alter the east and west migration And, judging by the extent of 

 modification the two elements among the plants have undergone 

 in New Zealand, I arrived at the conclusion that the tropical 

 migration, taken as a whole, was anterior to the Antarctic 

 migration. 



A study of the fauna confirms this opinion. For while in the 

 Malayan element we find a large number of endemic genera, the 

 Antarctic element consists largely of species which are found 

 elsewhere ; or, like the shags, are only slightly modified. This 

 shows that their spread has been later. 



This conclusion, however, does not prevent us from supposing 

 that some Antarctic immigrants may have been in New Zealand as 

 long or even longer than some Malayan immigrants. For there 

 may have been several periods of migration. 



Indeed, the Malayan element in the fauna shows considerable 



