| OCR Text |
Show 1892.] THE LAND-MOLLUSCA OF THE PHILIPPINES. 457 Bay in the N. and Illana Bay in the S., appears to me to represent the original channel of separation l. Corasia occurs all over the island ; its appearance and development must therefore have preceded the separating of the western portion. But Calocochlea and Eudoxus, the latter of which is almost peculiar to Mindanao, occur only in the N . and E. (e. g. smaragdina is found from Mainit in the extreme N. to Davao on the S.E. coast), and are not recorded from any point west of the narrow isthmus. Again, the section of Chloritis of which H. spinosissima, Semp., quieta, Reeve, and sanziana, H . & J., are well known examples, is almost peculiar to Mindanao, but is only found in the district to the W . of this peninsula, and does not appear to have penetrated the main portion of the island. One species of Corasia (zamboangce, H . & J.) is recorded from the island of Basilau (S. of Mindanao); the species is not peculiar, and occurs also on Mindanao. Mindoro.-The general relations of this island are very remarkable, and cause it to stand out as by far the most isolated of the whole Philippine group. A glance at the m a p might incline us to regard it as a link between Luzon and Panay, with close relations to the former island, and with no cause for especial individuality. Mindoro, however, is incomparably the most isolated of all the Philippines. It contains one, possibly two, absolutely peculiar subgenera, which are very well marked, and of which the nearest relations appear to be with Hypselostyla. In other words, the relations of Mindoro, are, so far, but only very remotely, with Panay. At the same time, however, no existing subgenus appears to be common to the two islands. Probably further exploration may detect Chlorcea, Corasia, and Calocochlea on Panay; but that would not bring its relationship to Mindoro at all closer, since these subgenera are known from almost every island. With Luzon Mindoro has, excluding the three subgenera universally prevalent, only one subgenus (Helicostyla) in common. All the species, however, are peculiar to Mindoro. Through this subgenus Mindoro appears also related to the Tablas- Romblon-Sibuyan group, and also to the Cuyos Is., but not to Panay. Axina, Eudoxus, Orthostylus, Phenyus, Canistrum, and Hypselostyla are completely absent. Cochlodryas, however, is common to Mindoro and Burias only. Cuyos Is.-These islands are very imperfectly known, but what little information we have tends to relate them with Mindoro, and not with Panay or Palawan. If Cuming's authority is to be trusted, the only two subgenera which occur in the Cuyos (Helicostyla and Prochilus) are common to Mindoro, but do not occur either on Panay or Palawan. Luban.-This little island, lying almost between Luzon and Mindoro, must have been, in all probability, isolated for a long time. It contains one well-marked subgenus, Ptychostyla, which is quite peculiar. Deep water surrounds the island on every side. 1 Most atlases, even the most recent, erroneously represent this isthmus as traversed by a lofty range of mountains. |
