376 BULLETIN 100, UNITED STATES NATIONAL MUSEUM. 



along eastern Luzon. The East Indian species Lionurus e rides is 

 closely related only to L. condylura of Japan. 



Only 11 species were obtained about the Sulu or Tawi Tawi Archi- 

 pelago, which separates the East Indian and the Philippine sub- 

 regions: 7 are found in the subregions on both sides, while 3 species * 

 were not dredged elsewhere; the Ilymenocephalus striatissim/us of 

 the Tawi Tawi region is intermediate between the East Indian //. s. 

 aeger and the Philippine II. s. torvus, but nearest //. s. aeger. 



B. THE PHILIPPINE SUBREGION. 



This subregion includes the waters about the central Philippine 

 Islands, north of the Tawi Tawi group, and south of west-central 

 Luzon, and exclusive of the Pacific Ocean along the east coast of 

 Luzon. While sharing many of its species with the East Indies, 

 this subregion is inhabited by a number of peculiar and often singular 

 forms: Bathygadus sulcatus; Gadomus magniftlis; C ory phaenoides 

 semiscdber (representing the East Indian C. tydemani) ; three species 

 of Cory phaenoides, each known only from its type dredged in the 

 depths of the Jolo (Sulu) Sea — namely, C. paradoxus, G. dubius, and 

 C. camarus; Coelorhynehus quincunciatus 2 and thompsoni, C. veJi- 

 fer, C. macrolepis, G. carinifer, G. acutirostris; Ilymenocephalus 

 gracilis (closely related to the Hawaiian II. tenuis) ; H. longiceps; 

 II. s. torvus (representing H. s. striatissimus of Japan, Formosa, and 

 eastern Luzon, and II. s. aeger of the East Indies ; intergrading with 

 striatissimus off northern and northwestern Luzon, and with aeger 

 about the Tawi Tawi group) ; Malacocephalus luzonensis 2 ; Ventri- 

 fossa macronemus (most nearly related to V. misakia of Japan and 

 eastern Luzon) ; Ventrifossa lucifer; Lionurus decimalis. 



The Philippine subregion appears to lack certain species of the East 

 Indies, as the Albatross failed to obtain them during months of in- 

 tensive dredging within the limits of the subregion. These species 

 follow: Bathygetdus fiIame?itosus., B. entomelas, Gadomus m.ultifilis, 

 Cory phaenoides asprellus, C. tydemani, C . heyningeni, G. aequatoris, 

 C. orthogrammus, C. sp. Weber, Coelorhynehus platorhynchus and 

 acantholepis, Hymenocephalus s. aeger, H. grimaldii, Malacocephalus 

 ? laevis, Lionurus infranudis, L. evides, L. vittatus, L. richardi, and 

 L. parvipes, Mataeocephalus adustus, Cetonurus robustus. 



In contemplating such a peculiar fauna occupying a comparatively 

 restricted area, one is led to examine the hydrographic data of the 

 region to determine whether the physical conditions of life may be 

 obviously unusual. Such an examination does, in fact, indicate that 

 the basic conditions of depth and temperature throughout this sub- 

 region are in peculiar relationship to each other. Briefly stated, the 



1 The closely related Coelorhynehus se^radintus, C. notatus, C. triocellatus. 



2 One specimen also dredged off eastern Luzon. 



