ARHNO. 327 



point of Arhno, for instance, the secondary lagoon will be formed by a 

 land rim on one side, leaving the face exposed to the action of the sea 

 more or less open. The islets in the vicinity of Dodo Pass are interesting 

 (Pis. 180, figs. 1, 2 ; 181, fig. 1) ; the inner line of islets, banks, and flats 

 and spits gives ns an excellent example of the manner in which a wide 

 reef flat becomes gradually covered with islands and islets, and finally may 

 become changed into a wide land rim by the movement of the material 

 carried backwards and forwards by the breakers, material which has been 

 supplied from the disintegration of the outer beach rock conglomerate, 

 from the corals thrown up on the sea face, or from the corals growing on 

 the slopes of the interior of the lagoon. The coarse shingle of the beaches 

 consists of rolled fi'agments of corals near the summit and at the base of 

 boulders which are scattered over the reef flat of the atoll ; this is fully 

 three quarters of a mile wide at low water at some parts of the land rim. 

 On the two sides of Dodo Pass the breakers sweep across the gaps between 

 the islands and islets (PI. 180, fig. 4) exposed to the action of the pi-evailing 

 wind, throwing a large amount of material into the gaps. Many of the 

 islands on the sea face between the northwest point and Dodo Pass are 

 covered by dunes blown westward over the rolled corals and coral heads 

 of the lagoon flat. Immediately east of Dodo Pass a large wooded island 

 has been formed on the inner side of the reef flat. The islands to the east 

 of Dodo are larger than those immediately to the west, and are separated 

 by wide gaps generally bare at three-quarter tide (PI. 228, fig. 4). On the 

 lagoon face of the islands are numerous bars of shingle or of sand at 

 right angles to them, running far into the flats;. these, little by little, 

 become covered with sand and vegetation. Dodo Pass is flanked on the 

 western face by a series of flats, shoals, islands, and bars ; on the northern 

 side they extend neaily three miles into the lagoon parallel to the north- 

 eastern and eastern coast. The ridge which forms the northern point 

 extends a considerable distance northward as a bank, with from three and 

 a half to six fathoms of water for a distance of over two miles north of 

 the reef flat. It is probable that the northern and northeastern points of 

 Arhno are spurs of the main ridge or summit upon which, after its 

 denudation, the atoll of Arhno has been built up. To the eastward of 



