3i8 A NATURALIST IN THE PACIFIC chap. 



In connection with the employment of the terms " upraised " 

 and " elevated " in the case of the Vanua Levu deposits I will take 

 this opportunity to remark that I do not thereby commit myself to 

 the view that there has been an actual upheaval of this region. 

 This is a matter, however, that will be found discussed in Chapter 

 XXVII. 



The Upraised Coral Limestones 



These reef-limestones are scantily represented in the island, 

 though one can scarcely doubt that they were once far more 

 extensive, having been largely stripped off by the denuding 

 agencies. They are mostly found on the south coast between 

 Naindi Bay and Fawn Harbour, and rarely extend to heights 

 greater than 20 or 30 feet above the sea, usually composing the sea 

 cliffs and not occurring as a rule inland. Massive corals are often 

 to be seen imbedded in their position of growth, as described in 

 Chapter II. ; and as far as the absence of signs of disturbance is 

 concerned, these ancient reefs might owe their present situation, 

 either to the withdrawal of the sea or to the upheaval of the land. 

 Such reef-limestones exist over much of the Pacific, and they 

 belong to the usual type of these rocks. 



Shelly and Foraminiferal Limestones 



These rocks are composed partly of reef-debris, partly of 

 volcanic detritus, and partly of the tests of foraminifera (usually 

 bottom forms), fragments of lamellibranchiate and gasteropod 

 shells, together with those of pteropods, and other organic remains. 

 Occasionally separate valves of the genera " Cardium " and 

 " Ostraea " are inclosed in the limestone. These rocks have been 

 evidently formed in rather shallow water. In places they overlie 

 palagonite-tuffs and clays, also foraminiferal. Similar limestones 

 are doubtless forming at the present time off the coast. 



They are usually hard in texture and greyish or pale yellow in 

 colour. They contain between 25 and 45 per cent, of carbonate of 

 lime ; whilst the residue consists of fragments of minerals (10 to 15 

 per cent.), including plagioclase, monoclinic and rhombic pyroxene, 

 and occasionally brown hornblende, with siliceous casts of foramini- 

 fera (4 to 20 per cent), mostly formed of chalcedonic silica but some- 

 times black and glauconitic ; the remainder (30 to 40 per cent.) 

 being composed of rounded and sub-angular portions of palagonite 

 and semi-vitreous basic rocks, of which the larger vary from 3- to i 

 millimetre in diameter. In some cases the carbonate of lime of the 



