232 "ALBATROSS" TROPICAL PACIFIC EXPEDITION. 



THE GILBERT ISLANDS. 



Plates 138-160, 223 ; 2%, figs. 3-6; f>26, figs. 1-3. 



The Gilbert Islands (PI. 223) follow much the same trend as the Ellice 

 Islands. They extend from Arorai to Taritari, about three degrees of 

 latitude on both sides of the equator. 



Three of the southern islands, Arorai, Tamana, and Nukunau are low 

 flat islands, and have no lagoons. Peru is a long, low flat island (PI. 226, 

 fig. 3), flanked by a narrow lagoon on the western side. Several of the 

 larger atolls of the group, Onoatoa, Tapeteuea, Maiana, Tarawa, and Taritari, 

 are noted for their open western faces, the western reef flats being more or 

 less submerged. In others, on the contrary, like Maraki and Aranuka, the 

 lagoons are nearly shut off from the sea, while such atolls as Apamama and 

 Apaiang remind us of similar atolls in the Paumotus. 



The soundings we took between the various islands of the Gilbert group 

 indicate the absence of a connecting plateau ; they are a series of isolated 

 peaks and ridges, separated by deep water, rising from very considerable 

 depths, as will be seen by examining our lines of soundings. Stations 190- 

 208 (PI. 223).^ We obtained 2221 fathoms between Apamama and Maiana, 

 1569 south of Tarawa, 2156 between Apaiang and Maraki, and 2255 fathoms 

 between Maraki and Taritari. The soundings also indicate that Apaiang, 

 Tarawa, and Maiana are the summits of a plateau with a depth of less than 

 500 fathoms, i-ising from great depths north and south of it (PI. 223). 



Our observations in the Gilbert and the Ellice Islands indicate that in 

 those districts where it is impossible or difficult to observe the structure of 

 the underlying platform, the coral reef question limits itself to the study 

 of the cutting down of the reef platform and of the land rim, of the 

 movements of the mass of material which rests upon the underlying 

 platform, whatever be its nature, the material being supplied by the 

 growth and decay of the corals, of the Nullipores and animals living upon 

 the reefs, either of the sea face or of the lagoon, and to following the endless 

 combinations resulting from the nature of the outer reef platform, and the 



' Mem. M. C. Z., XXVI, 1902, No. 1. p. 61. 



