(_d_) _The Philippine Province._--In the extraordinarily rich development of their Mollusca, the Philippines form a remarkable contrast with the poverty of the adjacent Malay islands. No less than 727 species of land Mollusca alone are known from the group, amongst which are included some of the finest and handsomest forms yet discovered. The main features of the fauna are Indo-Malay, with the addition of a certain Australasian element, and a remarkable development of individual characteristics. The principal indigenous feature is the profuse abundance of the genus _Cochlostyla_, a group of large and elegant land shells, partly helicoid, partly bulimoid in shape, many of the species of which are covered with a curious hydrophanous epidermis. They are in the main of arboreal habits, living in the tops of the enormous forests which cover the greater part of the islands. As many as 247 species, belonging to 15 sub-genera, have been described. [Illustration: FIG. 210.--_Cochlostyla_ (_Chrysalis_) _mindoroensis_ Brod., Mindoro, Philippines.] [Illustration: FIG. 211.--_Cochlostyla_ (_Orthostylus_) _Portei_ Reeve, Luzon. × ⅔.] The distribution of the sub-genera of _Cochlostyla_ on the different islands of the Philippine group affords important evidence on the geological relation of the islands to one another. Thus we find _Orthostylus_ and _Hypselostyla_ occurring in the central islands and S. Luzon, but not in Mindanao or Mindoro; we find _Chrysalis_ peculiar to Mindoro, _Prochilus_ to Mindoro and the Cuyos, _Ptychostyla_ to Luban, all these being sub-genera of very marked characteristics. Six out of the fifteen sub-genera are entirely absent from Mindanao, although occurring on the islands in the immediate vicinity. The little group Tablas-Romblon-Sibuyan are entirely deficient in certain sub-genera which occur on the islands surrounding them on all sides.[371] Other forms peculiar to the Philippines are _Diaphora_, a section of _Ennea_ with a curiously produced mouth, and several sub-genera of the Naninidae (_Vitriniconus_, _Vitrinoidea_, _Hemitrichia_). The great _Rhysota_ here find their metropolis. Another very marked group of _Helix_ is _Obbina_, 19 of the 25 known species being peculiar.