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Show 456 REV. A. H. COOKE O N [May 17, related to one another. They have no subgenus peculiar, but general relations are rather with Luzon than with the central islands. One species of Phengus indicates relations with Marinduque, while the complete absence of Hypselostyla, so common in Panay, separates them from the central group. Cebu and Bohol.-These islands, with Panay, are the metropolis of Hypselostyla, which has spread northward to Luzon. Both are sharply separated from Mindanao, since neither Orthostylus, which is abundant in Cebu and Bohol, nor Hypselostyla is represented in that island, while on the other hand Eudoxus, which is abundant in Mindanao, is entirely absent from Cebu and Bohol. Corasia is abundant in both islands; Axina is not recorded from Bohol, while it is abundant in Cebu, which indeed contains 6 out of the 10 existing species. Calocochlea, on the contrary, which is entirely absent from Cebu, occurs freely in Boholl. Panay.-This island appears, on a consideration of its fauna, to be rather isolated; but perhaps this may be accounted for by the fact that its nearest neighbour, Negros, has been scarcely explored. Its relations are with the central group, Hypselostyla being abundant and all its species peculiar to Panay. Orthostylus is the only other subgenus known to occur. Thus no connection is indicated with the Tablas-Romblon-Sibuyan group or with Mindoro. Mindanao (including Surigao and Camiguin).-This great island presents some remarkable features. Axina is entirely absent, while Calocochlea is exceedingly abundant. Corasia appears to be confined to the extreme S., where it is abundant. Phengus, Helicostyla, and Cochlodryas are absent, and, what is more remarkable, Ortho-stylus and Hypselostyla, so abundant on Cebu and Bohol, do not occur, thus indicating a very considerable severance between Mindanao and the central islands. The channel immediately north of Mindanao is not well surveyed, but appears undoubtedly to be of very considerable depth, 185 fathoms having been recorded by the ' Challenger ' close under the N. coast of Camiguin. The Surigao strait appears to be rather shallow on its eastern side, but as it opens out towards the west the depth appears rapidly to increase. A special feature of Mindanao is the development of Eudoxus, found elsewhere only in Luzon (?) and Catanduanes 2. So far as we can at present make out the relations of Mindanao are rather with Luzon than with the islands immediately contiguous. There seems every probability that the western part of Mindanao was once for a considerable time a separate island, completely disconnected from the central and eastern portions. The low and narrow neck of land, scarcely 20 miles across, lying between Iligan 1 Hidalgo (Journ. de Conch. 3e ser. xxvii. p. 175) gives Cebu as a habitat for calobapta, Jon. This must be a mistake, as the species is a Prochilus, which is confined to Mindoro and, perhaps, the Cuyos. 2 Hidalgo (Journ. de Conch, ut sup. p. 146) gives C. roissyana from "Surigao, clans File de Mindanao." I do not know any other authority for believing that roissyana is not peculiar to Mindoro. There is probably a misidentification of C. spheerion, Sowb. |