320 



NEW GUINEA AND ARU ISLANDS 



CHAP. 



further. Little is known of the fresh-water fauna. Melania 

 (28 sp.) is predominant, but on the whole the relations are 

 i\.ustralian rather than Indo-Malay. AinjniUaria is wanting, 

 while a decisive point of similarity is the occurrence of Isidora 

 (3 sp.), a genus entirely strange to the Oriental region, but 

 markedly characteristic of the Australasian. 



Land and Fresh-water 3Iollusca of Neiv Gruinea 



Waigioii is practically a part of New Guinea. Twelve 

 genera and twenty species of Mollusca are known, eight of the 

 latter being peculiar. The occurrence of Papuina^ Insidaria, 

 and Calycia sufficiently attest its Papuan relationship. Two 

 species each of Albersia, Chloritis, and Planispira occur.^ 



The Aru Is. are, as we should expect from their position, and 

 particularly from the configuration of the adjacent sea bottom 

 (see map), markedly Papuan. At the same time they show un- 

 mistakable signs of long-continued separation from the parent 

 island, for of their 36 land Mollusca 15, and of their 20 fresh- 

 water Mollusca 9 are peculiar. The Papuan element consists in 

 the presence of Papuina., Albersia, and Cristigibba. Moluccan 

 influence is not absent, for the three Helicina.^ the Albersia., and 

 one Cyclotus are all Moluccan species. The fresh-water fauna 

 appears to be a mixture of vaiied elements. The single 

 Segmentina is common to India, the Glaucomya to Malacca and 

 the Philippines, while the single Batissa is also found in New 

 Zealand. 



1 Mysol, with 2 ChJoritis, 1 Insularia, 1 Cristigibba, is decidedly Papuan. 



