16 ME. H. N. EIDLEY ON THE 



!Fresliwater mollusks occur in several islands, including Ma- 

 deira, where are a species of Ancyliis and Lymncea. The Azores 

 possess no freshwater mollusk according to Godman, who attri- 

 butes this to the paucity of waders and ducks inhabiting these 

 islands, although he gives a very considerable list of swamp-loving 

 birds as occasional migrants. In the Galapagos Islands a Paludina 

 occurs. 



Water-beetles are apparently always very rare in oceanic 

 islands. AVollaston shows that the Hydradephaga are the most 

 poorly represented group in the Atlantic islands visited by him 

 (Coleopt. Atlantidum, Introd. p. xv). In St. Helena, too, there 

 are none ; and in Fernando Noronha they seem scanty. 



DiSTEIBTJTION OF THE FaUNA COMPARED WITH THAT 

 OF THE FlOEA. 



It is unfortunate that the naturalists who have visited oceanic 

 or distant islands have usually examined into the distribution of 

 one group, either plants or animals, or often but one order of 

 the latter, so that it is very difficult to obtain any clear ideas as 

 to the relations of the two groups. I have had in presenting 

 these reports the assistance of my colleagues in the British 

 Museum, and other English naturalists of the highest standing, 

 and am therefore able to make a few observations on the distri- 

 bution of both plants and animals as compared together. 



Just as in plants, we have a considerable number of animals 

 introduced by man into the islands intentionally and by accident : 

 such, for instance, are the Gecko {HemidactyJus mahouia), the 

 American Cockroach {Blatta americana), and its curious parasite 

 JEvania, a spider, centipede scorpion, rats and mice, SitopUdus 

 oryzcB. These, though usually plentiful on the main island around 

 the houses, are markedly wanting from the smaller islets. 



There is also a large group which has arrived here by the aid 

 of their wings, probably assisted by a suitable wind. This 

 includes a number of the peculiar terrestrial fauna, the land- 

 birds and the insects. In looking over the lists of species 

 taken here, we may note that the smaller birds are endemic, and 

 a large proportion of the smaller insects. The small butterfly 

 and almost all the moths are know^n from the mainland of South 

 America, and the dragonflies are also widely distributed forms. 

 All the winged fauna have a South-American facies, whether they 

 are endemic or of wider distribution. 



