24 BIOLOGICAL SOCIETY OF WASHINGTON. 



represented by four species. There are also many other birds rep 

 resenting genera peculiar to New Zealand. Here also live the only 

 survivors (Sphenodon or Hatterid) of an order of reptiles (Rhyn- 

 chocephalia) which, in ancient times, had a wide distribution. The 

 fresh-water fishes are few, but noteworthy. One genus (Galaxias) 

 is common to the temperate portions of Australia and South Amer 

 ica, another (Prototroctes] to New Zealand and South Australia, a 

 third (Neochanna) of the family of Galaxiidse is peculiar, and also 

 peculiar is a genus (Retropinnd} distantly related apparently to the 

 Argentines (smelts, etc.) of the northern realms. The Gastro 

 pod mollusks, and other invertebrates exhibit a peculiar associa 

 tion of types, which, at the same time, re-enforces the distinctness 

 of the realm and gives rise to special problems of zoogeography. 



IX. THE NESOG^EAN REALM. 



The restricted Polynesian realm is distinguished by negative 

 rather than positive characters, and is to some extent a " refuge of 

 the destitute. ' ' It includes all the islands of the tropical portions 

 of the Pacific Ocean combined under the general name Polynesia. 

 It is distinguished from all others by the total or almost total 

 absence of indigenous types of mammals. The other common 

 .characters are very few; the avian types, on the whole, recall 

 mostly the Australian forms. There are, according to Wallace, 

 ''not more than about 50 genera and about 150 species of land- 

 birds. " It is possible that these islands are the remains of one or 

 more continental areas, and that at least most of them have been 

 submerged and lost their mammals, and on emergence, or rather 

 upheaval, have been peopled from other territories. The analysis 

 of this group would detain us too long, and this realm may, for the 

 present, be considered as a provisional one, to be hereafter studied 

 and properly limited. 



All the primary zoogeographical divisions recognized by Messrs. 

 Wallace and Allen have now been considered, but the relations of 

 the several realms to one another may be glanced at with profit. As 



