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Show 460 REV. A. H. COOKE ON [May 17, species of Ampkidromus are known from the Philippines (Sumatra 5, Java 15, Borneo 6) ; of these two get no farther north than Balabac, another occurs on Palawan, while two others are met with in Mindanao, and one of these has penetrated as far as Bohol and S. Leyte1. A detailed survey of some of the principal genera common to the Philippines and the neighbouring islands will be given below. It would seem as if the connection which probably at one time existed between Palawan, Busuanga, and Mindoro was not directly across the present Mindoro Strait, where the depth is extreme. The Cuyos Is. appear to have shallow water to the W., and decidedly deeper water to the E.; thus their connection is with Palawan now. Again, the water shallows rapidly towards the S.E. end of Mindoro Strait, and is broken by islets and submarine banks, which extend from the S. point of Mindoro towards Panay and also towards Busuanga ; the water, however, between these banks and islets is deep, being generally over 100 fathoms, and often more. The water off the N. and W . sides of Panay has not been very accurately surveyed, but is in all probability extremely deep. It would thus seem probable that any connection which may have existed between Mindoro and Busuanga (and a consideration of the very remarkable Helicidae of both islands makes such a connection extremely probable) followed the line of shallower water at the E. end of the Mindoro Strait, and possibly extended some distance eastward towards Panay. It will now be interesting to examine the Land-Mollusca of these two ridges, with a view of discovering whether or not they belong to the Philippine fauna. Unfortunately, our knowledge of the Land-Mollusca of the Soo-loo ridge is meagre in the extreme. W e know that Basilan, Lampinigan, and Malanipa are, by their Cochlostylce, closely related to Mindanao. W e know also that one species of Cochlostyla (lais, Pfr.) occurs on Soo-loo Is. Tawi-tawi2 is quite unexplored. The Mollusca of Bongao, the last island at the Borneo end of the chain, are known. Eleven species in all are enumerated, five of which show distinct relations with Borneo. The following species are known to occur on Basilan:- Cochlostyla zamboangce, II. & J. Also occurs in Mindanao. Xesta mindanaensis, Semp. „ Mindanao. Chloritis sanziana, H. & J. ,, Mindanao. Obbina rota, Brod. „ Bohol, Siquijor, &c. Rhysota semiglobosa, Pfr. „ Philippines generally. Macrochlamys crebristriata, Semp. Also occurs in Mindanao. Microcystis myops, Semp. & Dhrn. „ Philippines [generally. Trochomorpha metcalfei, Pfr. Also occurs in Philippines generally. Stenogyra panayensis, Pfr. „ Philippines generally. Pupina ottonis, Dohrn. „ Mindanao. 1 Amph. maculiferus, Sowb.; see Semper, Eeisen, II. iii. p. 148. 2 The ' Samarang' anchored off the island, but did not make a landing. |
