THE PHILIPPINES 



313 



element, and a remarkable development of individual character- 

 istics. 



The principal indigenous feature is the profuse al)undance of 

 the genus Coe/ilosfi/la, a group of large and elegant land sliells, 

 partly lielicoid, partly bulimoid in shape, many of the species of 

 wliich are covered with a curious iiydrophanous epidermis. They 

 are in the main of arboreal ha])its, living in the tops of the 

 enormous forests which cover the greater part of the islands. 

 As many as 1'47 species, belonging to 15 sub-genera, have been 

 descriljed. 



The distriljutiou of the sub-genera of Coehlostyla on the 



Fig. 2\0. —Coehlostyla (Chrij- 

 salis) mindorocnsis Brod., 

 Mindoro, Philippines. 



Fig. 2\l.— Coehlostyla {Ortho- 

 stylus) Fortei Reeve, Luzon. 



different islands of the Philippine group affords important 

 evidence on the geological relation of the islands to one another. 

 Thus we find Orthostylv.s and Hypselostyla occurring in the 

 central islands and S. Luzon, but not in Mindanao or Mindoro ; 

 we find Chrysalis peculiar to Mindoro, Frochilns 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, altliougli occurring on the 

 islands in the immediate vicinity. The little group Tal)las- 

 Romblon-Sibuyan are entirely deficient in certain sub-genera 

 which occur (jn the islands surroundins; them on all sides.^ 



^ A. 11. Cooko, P. Z. S. 1892, pp. 447-169. 



