364 "ALBATROSS" TROPICAL PACIFIC EXPEDITION. 



beach partly covered by coral sand. Owing to the depth over the barrier 

 reef flat ridge, no breakers were visible on the reef to the north of Uneyeute 

 Island until we came close to Unalik. Here, about the centre of the 

 northeast face, are a number of islands and islets on the edge of an 

 ill-defined plateau, with here and there shoal spots where corals have 

 been washed up. They are separated from the island of Onoupe, lying 

 to the north of them, by a pass with deep water ; a continuation of the 

 reef flat can be traced farther north, trending in a northwesterly direction. 



The shore of Onoupe is flanked by a shingle beach ; high cocoanut trees 

 grow on the island ; two islets are situated on the barrier reef flat, near 

 the northern point of the lagoon. At many points on the east and south 

 faces the presence of the reef flat is merely indicated by the difference in 

 color of the water covering the flat, and the occasional reef patches which 

 rise to the surface. The western horn of the atoll is occupied by the low 

 island of Ulul. The lagoon varies in depth from twenty to twenty-five 

 fathoms. Namonuito, Oraluk, and similar atolls represent the extremes of 

 the minimum development of a land rim, a mere thread of a narrow reef flat 

 encircling the lagoon, with only an occasional islet to indicate its presence.^ 



The atolls of the Mackenzie group are very similar in structure to 

 that of Namonuito, although the .shape of the atolls is somewhat different. 

 The same is the case with the Hall Islands, with West Faiu, Lamotrek, 

 Olimarao, Faraulep, Kama, and Ifalik ; wliile Feys (PI. 233, fig. 2), 

 Pikelot, and East Faiu are the oidy islands of the Carolines known cover- 

 ing nearly the whole reef flat upon which they have been thrown up, 

 that is, they are diminutive summits similar to the small islets in the 

 Marshall Islands, in the eastern part of the Pauraotus, and other groups in 

 the tropical Pacific. 



1 If the sketch of Oraluk on A. Chart 982 is correct the barrier reef flat of the atoll is by far 

 narrower than that of any atoll known to me. Some of the narrow barrier reefs of Tahiti may be 

 compared to Oraluk, 



