562 



H. B. GUPPY" ON THE RECENT 



its characters resembles the formation of Choiseul Bay, subsequently to be 

 described, apparently composes the bulk of the island of Alu. It is exposed in 

 the banks of the streams that open on the S.E. coast ; and may be followed up 

 in the higher parts of their courses in the interior, being also exposed in the 

 lower slopes of the inland ridges at an elevation of 200 feet above the sea. 

 Bedding is rarely well displayed on account of the limited character of the 

 natural sections, the beds displayed having, however, a gentle inclination. In 

 the mass it has the appearance of an argillaceous, earthy, moist rock, containing 

 the shells of Pteropods in abundance, such as Hyalcea, Diacria, Cleodora, 

 Creseis, together with numbers of Gasteropod and Lamellibranchiate shells, 

 such as Murex, Nassa, Hemicassis, Mitra, Natica, Dentalium. Foraminiferous 

 tests are present in profusion, the large tests of such as Cristellaria cultrata 

 and C. rotidata can be picked out by the fingers. The otoliths of fish are also 

 abundant. In addition, I found some simple corals referable to the deep-sea 

 genera, OdontotrocJius, Flabellum, Bathyactis (symmetrica ?), portions of the 

 shells of a sessile Cirriped ; and occasional leaves with their venation in a 

 condition of fair preservation. The Pteropods, bivalves, otoliths, and Foramini- 

 fera, are from their numbers most characteristic of this deposit. 



Mr Murray thus describes the characters and composition of specimens 

 of this deposit : — 



A very friable rock, chiefly composed of volcanic ashes with great numbers 

 of minute imbedded organisms, and resembling the " volcanic muds " in 

 character. 



Carbonate of Calcium (33 -67 per cent.), consists of Coccoliths, Otoliths, 

 Gasteropod and Lamellibranchiate shells, Pteropod and Heteropod shells, 

 Polyzoa, Serpulse tubes, Ostracode shells, Echinoderm fragments, and many 

 pelagic and bottom-living Foraminifera. (See list below.) 



Residue (66*33), brown, consists of — 



(a) Minerals (40-00), m. di. 0*5 mm., some particles 1*0 mm. ; felspar, 



magnetite, augite, hornblende, mica, quartz, &c. ; and a great many 

 glauconitic-like casts of Foraminifera. 



(b) Siliceous Organisms. — None noticed. 



(c) Fine Washings (26 - 33), argillaceous matter with fine mineral particles, 



and black fragments of organic matter. 



List of Foraminifera. 



Miliolina seminulum (rare). 

 Biloculina depressa ,, 

 Reophax pilulifera (very few). 

 Bulimina marginata (rare). 

 Pleurostomella alternans (few) 

 Chilostomella ovoidea (many). 

 Cristellaria rotulata (few). 



Cristellaria cultrata (few). 



calcar ,, 



aculeata ,, 



italica „ 



echinata „ 



vortex „ 

 Uvigerina tenuistriata (common). 



