362 SMITH. 



in Cebu, and contains the well lalo^v^l fossil Vicarya callosa Jeuks., which 

 occurs just above the coal in the Visaj-as and Luzon. 



Xext above the schist comes andesite, vrhich is the dominant rock in 

 the Zamboanga Peninsula. A large amount probably was derived from 

 an old vent now represented by Mount Panubigan, a peak of some 1,320 

 meters elevation, about eighty kilometers north of Zamboanga. This an- 

 desite so completely covers the underlying rocks that the occurrence of 

 schists and other formations in the Zamboanga Peninsula never before 

 has been noted by geologists. 



Wliile traversing a small stream back of San Eamon farm on the west 

 coast of the peninsula, I found pieces of schist included in the andesite, 

 which demonstrated that the latter was of later origin than the former, 

 and while in a molten state had caught up loose fragments of the underly- 

 ing formation and subsequently had cooled around them. The German 

 traveler and geogi'apher, Baron von Eichtofen, mentions the finding of 

 nmnmulitic limestone in a piece of float near Zamboanga. I also found 

 pieces of this float, but while I could see no Nummulites, I discovered 

 fragments of Orbitoides in it. I found none of this limestone in place. 

 However, back in the central and higher part of the range there may be 

 remnants of this formation. 



My observations on the Island of Basilan were limited to the northern 

 part in the vicinity of the town of Isabela. The hostile state of the 

 Moros at the time of my visit prevented much travel in the interior. 

 Wherever I went and as far as I could see from the boat, I found the 

 island largely covered by a mantle of andesite and basalt. It is a 

 densety wooded region with numerous volcanic cones and gentle slopes. 

 The soil is heavy and red. A tj^pieal specimen of basalt, exceedingly fine- 

 grained, was taken from the hill just back of Mr. Musser's plantation. 

 The chief minerals are plagioclase (labradorite and anorthite), augite, 

 olivine, and magnetite ; in addition, innumerable minute grains of highly 

 refracting substances occur which might easily be confused with any one 

 of the three minerals, zoisite, vesuvianite, and corundum. They are 

 almost colorless, have a bluish, sometimes greenish, cast, a high index 

 of refraction, low double refraction, and no pleochroism. I am of the 

 opinion that they correspond to the substance noted by Biiching in the 

 basalts from Breitfierst. The structure of this rock is pronouncedly 

 ophitic. Another rock obtained from Basilan, and which is found in 

 the old collection of the Spanish Mining Bureau, is a gabbro. This 

 consists of a perfect network of rods or lath-shaped plagioclases (oligo- 

 clase) with more or less granular pjTOxenes (diopside or diallage) in the 

 interstices or partially intergrown with the feldspars. There is also some 

 magnetite. The granular appearance of the pjTOxenes is due to the 

 basal cleavage. An analysis of Basilan gabbro is as follows : 



