CALCAREOUS FORMATIONS OF THE SOLOMON GROUP. 547 



to between 90 and 100 feet above the low-lying land at its base, and removed 

 inland a few hundred yards from the coast. Its interior has been excavated 

 into a suite of caverns known as the Waupa Caves. This was the greatest 

 thickness of coral rock that I saw exposed in the island of Ugi ; and I doubt 

 if it anywhere much exceeds a hundred feet. As one ascends the slopes of 

 the island this formation thins away, and only occasional fragments occur in 

 the red argillaceous soil. The greatest elevation at which I found the coral 

 rock was about 425 feet above the sea. 



The Soft Foraminiferous Deposit. — This rock, which is exposed in the ravines 

 and gorges excavated by the streams, forms the mass of the island. Closely 

 resembling the prevailing formation of Treasury Island, described in another 

 portion of this paper, it presents itself in the fresh condition as a chocolate- 

 coloured argillaceous and somewhat friable deposit, in which Foraminiferous 

 tests may be usually observed. It is often stained reddish-brown near the 

 surface through the hydration of its iron oxides. Specimens of this rock, after 

 being kept some time, become more friable and of a lighter colour. Subjoined 

 I have given the characters of this deposit with the list of the Foraminifera, 

 as determined by Mr Murray : — 



A friable rock of a greenish-blue colour showing minute organisms imbedded. 

 Its characters are those of the "volcanic muds" found in the "Challenger" 

 Expedition around volcanic islands. It seems to have been formed in com- 

 paratively shallow water, although not sufficiently near to the surface to permit 

 the reef corals to grow. 



Carbonate of Calcium (1393 per cent.) consists of Coccoliths, Rhabdoliths, 

 Gasteropod and Lamellibranchiate shells, Echinoderm fragments, calcareous 

 Alga?, and many pelagic and bottom forms of Foraminifera, {vide List). 

 Residue (86 '07) of a slate colour, consists of — 



(a) Minerals (50*00) m. di. 0-3 mm. a few larger ; felspar, magnetite 



(abundant), hornblende, augite ; many fragments of volcanic rocks 

 with pumice and glassy materials. 



(b) Siliceous Organisms (TOO) ; a few Sponge spicules. 



(c) Fine Washings (35*07), argillaceous matter, and many fine mineral 

 particles. 



List of Foraminifera, 



Planispirina celata (few). 

 Bolivina costata (rare). 

 Textularia quaclrilatera (rare). 

 Bulimina sp. (many). 

 Sagrina columellaris (common). 



„ striata (common). 



,, virgula (common). 

 Uvigerina asperula (few). 

 Globigerina bulloides (rare). 



„ „ var. triloba (common). 



Globigerina rubra (common). 



„ tlubia (few). 



,, inflata (few). 



,, conglobata (few). 

 Spbperoidina dehiscens (few). 

 Pullenia obliquiloculata (few). 

 Pulvinulina menardii (many). 



,, ,, var. tumida (many). 



Nonionina nmbilicatnla (rare). 

 Polystomella craticulata (rare). 



