350 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



shown by the specific characters of the organism to be Miocene. Although 

 a few of the rock-sections are composed of coral, and corals are also pres- 

 ent in some others, yet in the majority of cases they are absent ; Algae 

 and Foraminifera make up the bulk of the rocks. 



As regards the origin of the islands, this appears to have been some- 

 what as follows, according to Andrews (Bull. Mus. Comp. Zool., 

 XXXVIII.) : First of all in Tertiary times bedded limestones were 

 deposited on the ocean floor on which, in many cases (e. g. Mango), 

 volcanic materials, bursting through, were heaped. Wherever the 

 accumulations reached sufficiently near the surface, corals began to grow 

 and to form a reef. Intermittent elevation followed, each pause allow- 

 ing the corals to form a new reef growing seawards on its own talus, and 

 which, on further elevation, was transformed into a raised terrace. A 

 succession of terraces is formed in this manner, amounting in the case 

 of Yathata to as many as six, whilst the modern reefs, should elevation 

 be repeated, will form another. The foundations of the terraces may 

 be the bedded limestones and volcanic accumulations, or very often 

 masses of rubble representing the talus derived from the terrace itself. 

 The rubble at Xiue is bedded and dips towards the sea at an angle of 

 about 40 °. It will be seen from the mode of origin that whilst the 

 oldest terrace is the highest one, and the rubble foundations are of the 

 same age as the terrace immediately above, the bedded limestones form- 

 ing the core of the island follow the ordinary rule that the oldest bed 

 is at the base. 



The organisms found comprise fifteen genera of Foraminifera, with seven 

 other genera doubtfully present, besides algae, corals, echinoderms, mol- 

 lusca, including Tunicata and Polyzoa, with an occasional annelid. The 

 genera of Foraminifera are as follows :. — 



Miliolina, Orbitolites, Textularia, Gaudryina, Globigerina, Planorbulina, 

 Discorbina, Truncatulina, Carpenteria, Polytrema, Tinoporus, Gypsina, 

 Amphistegina, Heterostegina, and Orbitoides. 



The genera doubtfully present are : Ammodiscus, Hastigerina, 

 Sphoeroidina, Spirillina, Pulvinulina, Calcarina and Anomalina. 



For aid in the determination of doubtful forms I have to thank Mr. 

 F. Chapman, who has given me valuable assistance. 



FIJI. — Mango. An island of composite structure composed partly 

 of limestone and partly of volcanic rocks. It has been upheaved to the 

 extent of about 500 feet, and there are remains of a terrace at about 200 

 feet, showing a pause in the elevation. 



