POLYNESIAN REGION. 397 



15, Polynesian Region. 



Tlie Pacific Islands are partly the volcanic summits of submerged moun- 

 tain ranges, usually fringed or surrounded with coral reefs ; and partly atolls 

 or lagoon islands, scarcely rising above the sea and presenting no vestige of 

 the rock on which they are based. The low coral-islands form a long stream 

 of archipelagos, commencing in the west with the Pelews, Cai'oliues, Radack, 

 Gilbert, and Ellice groups, then scattered over a wider space and endiug 

 eastwards in the Low Archipelago ; they are chiefly, perhaps entirely, colo- 

 nized by drift from the other islands. 



The volcanic groups are the Ladrones, Sandwich Islands and Marquesas, 

 to the north of the low coral z jne ; and to the south of it, the Salomons, New 

 Hebrides, New Caledonia and Feejees, — the Friendly Islands, Navigator's and 

 Cook's Islands, — Society and Austral Islands, ending with Pitcairn's and 

 Elizabeth Island. Many of these are very lofty, and are perhaps the most 

 ancient land in the world.* Their molluscan fauna is entirely peculiar, but 

 it has most afhuity with those of New Zealand and the Asiatic Islands, and 

 great analogy with those of St. Helena, Brazil, and the W. Indies. 



Salomons — Neiv Hebrides— New Caledonia — Feejees. 



The most remarkable land-shells of these islands are the great auriculoid, 

 Bulimi (e, g. B. auris-hovina and B. miltochilus of the Salomons). Acicula 

 striata and 2 sp. of Cyrena are found at Vanicoro ; and Physa sinuaia 

 Peroniaacinosa diwdi corptilenta, and several Neritinas and coronated Melanias 

 have been obtained at the Feejees. f 



Helix 18 Bulimus 10 Cyclopborus 2 



Nanina 2 Partula 6 Omphalotropis 1 



Vitriua 6 Acicula 1 Helicina 6 



Friendly Islands — Navigator's — Society Islands. 

 The principal lofty and rocky islands of the southern Pacific, at which 

 land-shells have been obtained, are Tonga, Samoa, Upolu and Manua; 

 Taheiti, Oheteroa, and Opara ; Pitcairn's Island and Elizabeth Island. 

 Each appears to have some peculiar species and some common to other 

 islands; the little raised coral islet Aurora (Metia) N. E. of Taheiti, 250 

 feet in elevation, has four land snails which have been found nowhere else ; — 

 Helix pertenuis, dcedalea, Partula pusilla, Helicina trochlea. " Samoa and 

 the Friendly Islands must have intimate geological relations ; the same forms, 

 and many of the same species of land-shells occur on both groups ; not a 

 single Feejeean species was collected on either."— (Gow/<r/.) 



* Islands composed partly of stratified rocks must be newer than those rocks; 

 Volcanic Islands may be of any degree of antiquity. 



t The Feejees (Viti) axe more nearly allied to the westward islands, such as the 

 New Hebrides, than the Friendly Islands. Succinea and Partula, so plentiful at the 

 latter, are not found at the Feejees.— (Gould, U. S. Exploring Expedition,) 



