2o6 A NATURALIST IN THE PACIFIC ch. xiv 



and Tukavesi, where the mountains rise close to the beach, occur 

 basic agglomerates and agglomerate-tuffs, derived from basaltic 

 andesites. A specimen of the last named represents an uncommon 

 type of basaltic rock (sp. gr. 2'8s), which on account of the character 

 of the felspars and of the pyroxene of the ground mass is referred 

 to the prismatic sub-order of the orthophyric order of the 

 hypersthene-augite andesites (page 290). 



It may be inferred from the foregoing remarks that whilst the 

 main elevated mass of the Ngala Range is composed of altered 

 basic andesites, the product of ancient eruptions, the basic agglomer- 

 ates, tuffs, and clays, which occur on the lower slopes and in the 

 outlying spurs, are of later date. These tuff's and clays are evidently 

 of submarine origin, at least in the lower levels ; but although 

 fossiliferous deposits were not observed at greater elevations than 

 300 feet above the sea, it is probable that future investigators will 

 find them at much higher levels. Their discovery, as before 

 noticed, at an elevation of 1,100 feet in the adjacent Waikawa 

 mountains, renders it likely that as in the case of the mountainous 

 districts of the main portion of the island the whole of the Natewa 

 peninsula was at one time submerged, or at least all the region 

 excepting the summit of Mount Ngala. 



