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Show 1892.] ON THE LAND-MOLLUSCA OF THE PHILIPPINES. 447 6. O n the Geographical Distribution of the Land-Mollusca of the Philippine Islands, and their Relations to the Mollusca of the neighbouring Groups. By the Rev. A. H . C O O K E , M.A., F.Z.S., Fellow and Assistant-Tutor of King's College, Cambridge. [Eeceived April 20, 1892.] The Land-Mollusca of the Philippines may be regarded as consisting 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 development lies to the S.W. or the S.E. of the Philippine group. The object of the first part of this paper is to examine the distribution of the genus Cochlostyla 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 Land-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 between several of them is somewhat arbitrary. 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 of Cochlostyla. I have followed Semper2 in regarding Axina and Corasia as true Cochlostylce, and von Mollendorff in adding 3 Chlorcea and4 Ptyeho-styla and excluding s Phcenicobius. Semper admits that the only distinction between Cochlostyla and Chlorcea is that the latter exhibits some small anatomical difference in the genital apparatus, and this, as von Mollendorff justly remarks, is hardly sufficient reason for keeping it separate. The division of subgenera adopted by Semper 1 About 240 are enumerated by Hidalgo, ' Journ. de Conch.' 3e ser. xxyii. 1887, pp. 111-192 ; but the list might be considerably narrowed by the reduction of many "" species "'to the rank of varieties, and the exclusion of sereral which are not true Cochlostylce. 2 ' Eeisen,' II. iii. pp. 190, 166. 3 Nachr. mal. G-esell. xx. 1888, p. 99. 4 Ibid. p. 65. 5 Ibid, xxiii. 1891, p. 200. |