36 "ALBATEOSS" TROPICAL PACIFIC EXPEDITION. 



Brander and Mohican Islets (PI. 205, fig. 3), which project partly across 

 the western side of Avatoru Pass, and Nui Nui Islet, which holds the same 

 position to Tiputa Pass (PI. 204, fig. 3), show the whole process o£ disinte- 

 gration and erosion of the old tertiary coralliferons limestone to below low- 

 water mark. During this erosion it has, not been planed off uniformly ; 

 some parts have been more easily washed away, leaving ledges and ridges 

 of the old rock, and the spaces between them have been filled by the 

 formation of the recent beach rock, breccias, and conglomerates (Pis. 8, 

 fig. 2; 9, fig. 1; 11). The former greater extent of these islands and 

 islets is indicated by the prolongation lagoonward of the inner platform, 

 on which are still found here and there boulders of the old reef rock 

 (Pis. 9, fig. 2; 13, fig. 2), resting upon it, associated with boulders of the 

 modern beach rock gradually passing into the modern reef flat. 



The vegetation on the lagoon side of the outer land rim is usually more 

 luxuriant (PL 6, fig. 1) than on the sea face, and immediately behind the 

 highest part of the beach slope (PI. 5), where the shrubs and bushes and 

 trees are exposed to the more violent winds which sweep in from the sea. 

 It is remarkable how uniformly the winds and seas follow the outline of 

 the lagoon, making it quite difficult, from the prevailing swell, to effect a 

 landing, except under very favorable conditions, on the sea face of the lee 

 islands of an atoll. 



The bottom of the lagoon at our anchorage in 9f fathoms consisted 

 of incrusting NuUi pores and coralline Algae, forming, ' as a general 

 rule, a hard coating upon the bottom. Similar bottom was found 

 everywhere in the lagoon on the line from , Avatoru Pass to Tiputa Pass, 

 and on the line carried across the lagoon by Lieutenant Rodman from 

 our anchorage to the weather side of the atoll (PI. 204, fig. 4). A few 

 shoals were found, and an islet (PI. 19) similar in its structure to the islet 

 west of Mohican Island. The soundings varied from 14 to 17 fathoms 

 (PI. 204). The bottom consisted entirely of hard Nullipore growth. 

 Nothing came up in the boat dredge, and the depth was quite uniform. 

 The same hard Nullipore bottom appears to cover the bottom of the lagoon 

 wherever there are no coral patches. Corals occurred in the lagoon in exten- 

 sive patches in from two and three to 10 fathoms of water, both along the 



