Rhytida 1 Helicarion 2 Rhysota 1 Hemiplecta 11 Xesta 2 Microcystis 3 Microcystina 2 Sitala 2 Oxytes (?) 2 Conulus 1 Trochomorpha 8 Nanina (?) 3 Charopa 1 Thalassia 3 Ochthephila(?) 1 Chloritis 13 Planispira 5 Cristigibba 9 Insularia 17 Obbina 1 Albersia 3 Hadra 4 Pedinogyra 1 Papuina 35 Corasia (?) 1 Bulimus (?) 1 Calycia 4 Partula 3 Pupa 1 Stenogyra 1 Tornatellina 1 Perrieria 1 Succinea 1 Vaginula 1 Limnaea 2 Isidora 3 Melania 28 Faunus 1 Vivipara 4 Diplommatina 1 Pupina 4 Pupinella 3 Omphalotropis 2 Bellardiella 2 Leptopoma 16 Cyclotus 5 Cyclotropis 5 Helicina 15 Unio 4 Cyrena 3 Corbicula 1 Batissa 8 _Waigiou_ 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_, _Insularia_, and _Calycia_ sufficiently attest its Papuan relationship. Two species each of _Albersia_, _Chloritis_, and _Planispira_ occur.[372] 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 unmistakable 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 varied 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. _Land and Fresh-water Mollusca of the Aru Islands_ Xesta 4 Microcystis 1 Hyalinia(?) 1 Trochomorpha 1 Patula 1 Eulota 1 Chloritis 5 Cristigibba 2 Albersia 1 Papuina 4 Pupa 2 Stenogyra 2 Planorbis 1 Segmentina 1 Melania 14 Leptopoma 3 Moussonia 1 Realia 1 Cyclotus 3 Helicina 3 Cyrena 2 Glaucomya 1 Batissa 1