326 "ALBATROSS" TROPICAL PACIFIC EXPEDITION. 



of the west side, with their sand spits and bars, forming the southern 

 edge of the secondary lagoon of the northern point (PI. 182, fig. 2). 

 The secondary lagoon must be of considerable depth, judging by the 

 dark blue color of the water. The northern extension of the two sides 

 of the secondary lagoon is indicated by a mere thread of breakers and 

 of discolored water, showing the extension of the reef flat as it passes 

 into the deeper bank off the northern point of Arhno (PI. 228, fig. 4). 



The islands of the Avest face extend about five miles south of the base of 

 the secondary lagoon of the northern spit ; they are on the very edge 

 of the wide reef flat. On the lagoon side of the flat exists here and 

 there a huge sand bar connected with the outer shingle beach forming the 

 west face of the land rim. The islands and islets are separated by wide 

 gaps, edged by shingle beaches, the sand spits running towards the lagoon 

 forming wide, exceedingly shallow bays. We skirted for a considerable 

 distance along the west face of the narrow outer reef flat of the islands. 

 The position of the wide reef flat which forms the northern part of 

 the western side of the atoll is indicated by the reach of greenish or 

 light green water extending eastward into the lagoon. 



Along the northeast face of Arhno, from the northwest point to Dodo 

 Pass, bars run at an angle across the wide reef flat, with a number of 

 islands and islets and spits, connected at half-tide by beach rock con- 

 ,glomerate and shingle. The outer reef flat is comparatively narrow, but 

 on the west side the lagoon flat is wide, and there are from two to 

 three lines of islands and sand bars and sandy islets on the lagoon reef 

 flat immediately north of Dodo Pass (PI. 180, fig. 4). 



The islands are flanked on the lagoon side by beach rock conglomerate 

 surmounted with coral shingle on the outer face of the reef platform, and 

 with fine coral sand on the inner side of the reef flat. These islands and 

 islets become gradually connected, forming a series of irregular parallelo- 

 grams enclosing shallow basins; these finally become filled up, forming a 

 wide island extending more or less diagonally across the reef flat. When 

 this process has taken place on the flat of a point, as, for instance, the 

 northwest point of Likieb, the point will gradually be filled up, and thus 

 a secondary lagoon be formed. Should this take place on the northeastern 



