196 LAND REGIONS. 



north of the equator (Mariannes, Pelew, Carolines, etc.), and the 

 austral islands, south of the equator (Samoa, Tonga, Cook, Tahiti, 

 Paumotus, Gambler, etc). 



Throughout the entire region the terrestrial species are of 

 small size ; Placostjdus, Geotrochus and Cochlostyla disappear. 

 The heliciform shells belong to the genera Patula, Endodonta, 

 Trochomorpha, Nanina, Microcystis, etc., whilst the operculated 

 pulmonates are represented by Diplommatina, Realia, Pupina, 

 Helicina. The terrestrial species are generally localized. 



The Sandioich Islands. These contain nearly 400 nominal 

 species, of which the three genera Achatinella, Auriculella and 

 Carelia, closely related, are peculiar to this group. Achatinella 

 alone has 288 species, or varieties, some of which are always 

 dextral, others sinistral, and others again either dextral or 

 sinistral. Limnsea is here sinistral. The progress of agriculture, 

 disappearance of some of the indigenous trees, and introduction 

 of cattle combine to diminish the Achatinellse, some of the species 

 of which are upon the verge of extinction. 



The Fartula Islands. In the Pelew Islands occurs a very 

 curious fauna, characterized by numerous species of Diplomma- 

 tina of the section Palaina. There are three Partulas. 



The Mariannes or Ladrones contain 4 Partulas, etc. About 

 twenty -five species, including a Partula inhabit the Carolines. 



The Ellice and Samoa Islands appear to possess the same 

 fauna, aggregating seventy-six species. The heliciform shells 

 are of small size and belong to the genera Nanina (groups 

 Microcystis, Trochonanina, Gastrodonta), Patula (Endodonta), 

 Trochomorpha, etc. The geniTS Partula contains five species ; 

 there are four Cyclophorus (group Ostodes). The fresh-water 

 shells include Melania, 11 sp., Neritina 13 sp., Navicella, 4 sp. 



The Tonga Islands have about 50 species, a few of which are 

 common to the Samoa and Yiti Archipelagos. The Cook and 

 Hervey Islands have 16 species of Patula, Endodonta, 3 of the 

 curioiis genus Diadema, etc. 



The Tahiti or Society Islands possess a very rich molluscan 

 fauna, embracing 130 species. This is the metropolis of the 

 genus Partula, which numbers 45 species here, besides the few 

 found in other islands. There are 16 species of Endodonta, 10 

 of Realia, 10 of Helicina, 6 Melania, 7 Neritina, etc. Very little 

 is known conchologically of the Paumotus and Gambler Islands, 

 and not much more of the Marquesas ; each of these groups 

 contains a few Partulas. 



20. New Zealand Region. 



Although the islands of New Zealand contain a large number 

 of peculiar mollusks, there are generic analogies with Australia 

 in the occurrence of Paryphanta, Athoracophorus and Rhytida, 



