vm,A,5 Pratt and Smith: Petroleum Resources 309 



Matataja and Vigo Rivers and is separated from the coastal 

 ridges on both sides by other erosional valleys. To the south- 

 east the plateau is not perfectly detached from the coastal ridge, 

 the intermediate valleys being shallow. 



The southern termination of the interior plateau is at some 

 distance from the seashore, and a strip of low ground, several 

 kilometers wide, intervenes between it and Bon doc Head (ele- 

 vation, 392 meters) — a conspicuous landmark for navigators 

 rounding the southern point of the peninsula. 



Mount Maclayao, 398 meters in height, is the most prominent 

 elevation in the north-central part of the field. It is really a part 

 of the west coast ridge, although it extends eastward into the 

 interior, and forms an area of high ground common to the head- 

 waters of the main drainage systems north of the plateau region. 



HYDROGRAPHY 



The main streams debouching upon the lateral coasts are con- 

 fined in comparatively narrow valleys near their mouths. Where 

 erosion is well developed, their middle courses are meandering 

 and are bordered by wide flat terraces of alluvium. The main 

 lines of flow follow the trend of the peninsula, so that streams 

 working back from the east and west coasts attain relatively 

 short lengths in the direction of their lower courses, but develop 

 their principal tributaries at right angles on each side, draining 

 long strips of territory to the northwest and southeast. Vigo 

 River, for example, flows almost east into the sea at its mouth; 

 but its largest affluent, Malipa Creek, flows north for a distance 

 greater than the length of the Vigo below the junction of the 

 two. Tagatay River, or the upper part of the Vigo, flows south- 

 east for a distance equal to the length of the lower east-flowing 

 portion of the stream, and other large tributaries come into 

 Vigo River from the northwest. 



Pagsanhan and Talisay Rivers, which empty into the sea on 

 the southern coast, flow throughout their lengths in compara- 

 tively straight lines. Talisay, or Malumbang River, and Silon- 

 guin, or Canguinsa River, 9 are remarkable in having no important 

 tributaries. In the plateau region these rivers and the Amoguis 

 branch of Pagsanhan River flow through narrow canons. Bahay 

 River also has a deeply eroded valley, but has developed large 

 tributaries. 



Ayoni, Matataha, and Mulanay Rivers are formed of several 



* In the native usage a river assumes the name applied to the locality 

 through which it flows; consequently the same river may have several 

 different names. 



