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 sixth 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, and 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 
zeo-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 fauna, 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, I propose to offer briefly for consideration the grounds 
which seem to me 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 
XXIII.) 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 {rom any connexion with the Philip- 
‘Nature,’ Noy. 1888, pp. 37, 38. 
