92 "ALBATROSS" TROPICAL PAriFIC EXPEDITION. 



face, where there are but three small islands with sand bars on the shallow 

 submerged reef (PI. 57, figs. 1, 4). 



On the central part of the west shore there is a wide reef flat partially 

 covered with beach rock scattered over the surface of the old ledge in innu- 

 merable boulders, especially near the sea face. Gaps of varying width 

 follow one after another in quick succession as the separate islands make 

 their appearance along the western face of the atoll. Many of the gaps 

 are not more than 30 or 40 feet wide. The sea face of the islands is 

 usually flanked by coral shingle beaches, while the lagoon beaches con- 

 sist of coral sand (Pis. 56. figs. 2, 3 ; 57, fig. 2). Bars of sand seem to be 

 forming both on the lagoon side and in the cuts, the .sand piling up on 

 the lagoon edge of the flats (PI. 56, fig. 2). The island at the southwest 

 point has a high shingle beach (at least six to seven feet), the other islands 

 to the north have low shingle beaches (Pis. 57, fig. 2 ; 58, fig. 2), not 

 higher perhaps than three to four feet. 



A wide reef flat extends on the lagoon side of the i.slands, more than a 

 third of a mile in width (PI. 57, fig. 4), and at the northern extremity of 

 the atoll, this flat is covered by a large island occupying its horn, and fully 

 1000 feet wide (PI. 56, fig. 1). 



At the base of the shingle beaches of the islands, on the western rim 

 of the atoll, are accumulated masses of large boulders (Pis. 56, figs. 1, 2 ; 

 57, fig. 3 ; 58, fig. 2), many of them beach rock or recent conglomerate ; 

 other boulders are outcrops of the old ledge which forms the underlying 

 base of the atoll, and which have not been concealed by the mass of recent 

 material thrown up on the surface of the outer platform. 



The whole of the shore of the north point is thickly covered with 

 large boulders, many of them undercut on one side, forming so-called horse- 

 heads, — parts of the old ledge still attached to old ledge reef platforms. 

 The tinted NuUipores and red or pink and blue Pocillipores color the knolls 

 forming the outer raised edge of the reef platform. On the northern part 

 of the east face the reef flat is w^ide, fully 1500 feet from the base of the 

 shingle beach flanking the northern island, and slightly dished (PI. 56, 

 fig. 1), it is full of sinks and pot-holes. At the base of the shingle beach 

 run stretches of beach rock, recent conglomerate, and outcrops of old ledge. 



