1892.] ON THE LAND-MOLLUSCA OF THE PHILIPPINES. 447 



6. On the Geographical Distribution of the Land-MoUusca 

 of the Philippine Islands, and their Relations to the 

 MoUusca of the neighbouring Groups. By the Rev. A. 

 H. Cooke, M.A., F.Z.S., Fellow and Assistant-Tutor of 

 King's College, Cambridge. 



[Received April 20, 1892.] 



The Land-Mollusca of the Philippines may be regarded as con- 

 sisting of two classes, those belonging to peculiar genera or subgenera 

 developed after the final separation of the group, and those belonging 

 to genera or subgenera common to the neighbouring islands. These 

 latter may again be subdivided into (1) Indo-Malay and (2) Moluccan 

 and Polynesian genera, according as the metropolis of their deve- 

 lopment lies to the S.W. or the kS.E. of the Phihppine group. 



The object of the first part of this paper is to examine the distri- 

 bution of the genus CocTilostyla amongst the different islands of the 

 Philippine group. The Philippines are distinguished from every 

 other group throughout the Pacific, except the Sandwich Islands, by 

 the possession of an almost wholly peculiar and very conspicuous genus 

 of Laiid-Mollusca, of striking beauty in form and ornamentation, and 

 exceedingly rich in species \ The genus falls into 15 subgenera, the 

 majority of which are on the whole fairly well marked, although the 

 distinction betweeu several of them is somewhat arbitrarv. Not a 

 single island is without its representative of the genus, and the 

 species and even the subgenera are frequently much restricted in the 

 area of their distribution. The whole genus thus forms an interesting 

 clue by which to examine the problem of the ancient relationship of 

 the different islands to one another. 



Preliminary Remarks on the Subgenera o/Cochlostyla. 



I have followed Semper ^ in regarding Axina and Corasia as true 

 CochlostylcB, and von MoUendorff in adding ^ Ch/oraa and ' Ptyolio- 

 styla and excluding ' PAce«ico6!MS. Semper admits that the only 

 distinction between Cochlostyla And Cklorcea is that the latter exhibits 

 some small anatomical difference in the genital apparatus, and this, 

 as von MoUendorff justly remarks, is hardly sufficient reason for 

 keeping it separate. The division of subgenera adopted by Semper 



^ About 240 are enumerated by Hidalgo, ' Journ. de Conch.' 3'' aer. xxvii. 

 1887, pp., 11 1-192 ; but the list might be considerably narrowed by the reduction 

 of many " species" to the rank of varieties, and the exclusion of se/eral which 

 are not true Cochlostylm. 



- ' Eeisen,' 11. iii. pp. 190, 166. 



^ Nachr. mal. GeseU. xx. 1888, p. 99. 



* Ibid. p. 65. 



« Ibid, xxiii. 1891, p. 200. 



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