1889.] RELATIONSHIPS OF PALAWAN ISLAND. 221 



indebted for our first acquaintance with the fauna of the islands in 

 question,has given formal expression, in a prominent scientific journal', 

 to the view that Palawan and Balabac should be considered as con- 

 stituting, zoologically, a part of the Philippine Archipelago. Prof. 

 Steere, having proceeded to divide the Philippine " Province " of 

 the Indo-Malayan Sub-Region into six " Sub-Provinces," of which 

 the sixtli or Western Sub-Province "includes Balabac, Palawan, and 

 perhaps the Calamianes," goes on to state that " this Sub-Province 

 has evidently received a large portion of its fauna from North Borneo, 

 through Balabac, at a comparatively recent date, aud since its separa- 

 tion on the north from the rest of the Philippines, so that these 

 genera have not flowed over into Mindoro and Luzon. In addition 

 to these apparently late arrivals from Borneo, the Sub-Province 

 possesses a large number of peculiarly Philippine birds and mammals, 

 which show it to be an integral part of the province." So that it 

 would seem from the above extract that, in Prof. Steere's opinion, the 

 fundamental characteristics of the fauna of the Palawan group of 

 islands are Philippine rather than Bornean, although there has been 

 a comparatively more recent and very considerable invasion of Bornean 

 forms ; and the group is thus for the first time pronounced to be 

 zoo-geographically, as it is politically, an integral portion of the 

 Philippine sub-area. 



With this view I do not find myself able to concur, and it seems 

 to me that such evidence as is available on the subject indicates 

 rather that Palawan and the other islands mentioned by Prof. Steere 

 have never been directly connected with any part of the Philippines 

 since the former received their existing population, but that they have 

 been almost certainly so connected with Borneo, or, more correctly 

 perhaps, with a south-eastern extension of continental Asia, of which 

 Borneo formed a part, It appears to me that it was from the Bornean 

 side that these islands received their original fauaa, and that the Phi- 

 lippine element is the foreign element and the one of comparatively 

 recent advent. As it is very desirable that the natural relationship of 

 the Palawan group should be placed on an established footing as soon 

 as possible, 1 propose to offer briefly for consideration the grounds 

 which seem to nie to justify the definite inclusion of these islands in 

 the western sub-area of the Indo-Malayan Sub-Region. 



A glance at the accompanying map of the Palawan group (Plate 

 XXIil.) demonstrates at once that these islands, together with 

 Cagayan-Sulu and Sibutu (which have been also looked upon as 

 zoologically Philippine until recently), are all intimately connected 

 with Northern Borneo by a very shallow submarine bank, the depth 

 of the sea on which is generally less than 50 fathoms, and nowhere 

 exceeds 100 fathoms continuously through the straits intervening 

 between the China and Sulu seas. At the 100-fathom limit the 

 bed of the ocean abruptly plunges down to depths ascending, in the 

 Mindoro and Sibutu straits, 500 fathoms, and in the Sulu sea 1900 

 fathoms, thereby forming a profound gulf, which completely severs 

 all the islands above mentioned I'rom any connexion with the Philip- 

 ' ' Nature,' Nov. 1888, 'pp. 37, 38. 



