PARTULA. 167 



age. Their distribution is what would be expected were the 

 present archipelagos remnants of a former continent, now iso- 

 lated by subsidence. This continent, from the absence of all of 

 the higher families of land snails on the islands remaining, I 

 have conjectured to have been isolated since Palaeozoic times, 

 though the final dismemberment of its various components 

 was doubtless much later. (See Pilsbry, The Genesis of 

 Mid-Pacific Faunas, Proc. Acad. Nat, Sci. Phila. 1900, p. 568) . 

 Such groups as the Society Islands or Fijis may well have 

 existed as rather large land masses as late as middle Tertiary 

 times. Indeed, this hypothesis would seem to be an essen- 

 tial part of any attempt to explain the distribution of land 

 snails in most of the groups of high islands. 



The most convenient grouping of species for the purposes 

 of this monograph is by geographic range. The following 

 divisions are used. 



I. Marquesas Islands, species 1 to 6. 



II. Society Islands, species 7 to 50. 



III. Austral and Hervey Islands, species 9, 52. 



IV. Samoan Islands, species 53 to 60. 



V. Fiji Is., Kotuma and Tonga Is., species 61 to 63. 

 VI. New Hebrides and Santa Cruz groups, species 64 to 80. 

 VII. Solomon Islands, species 81 to 91. 

 VIII. New Ireland, New Britain, etc., and Admiralty Is., 



species 92 to 96. 

 IX. Louisiade Archipelago, including Trobriand and 



Woodlark Is. ; New Guinea, Species 97 to 100. 

 X. Talauer Is., species 101. 

 XI. Pelew Islands, species 102 to 104. 

 XII. Caroline Islands, species 105 to 108. 



XIII. Marianne Islands (Guam), species 109 to 111. 



XIV. Snails of other genera described as Partulse. 



XV. Species of uncertain or unknown habitat, species 12, 

 21, 47, 48, 49, 50, 51, 60, 72, 86, 94. 



