74 "ALBATROSS" EASTEllN TKOPICAL PACIFK^ EXPEDITION. 



" miki miki.' Tlic lower figure of the same plate shows the eastern face 

 of Manga Reva Island seen through a gap in the lagoon sand Ijeach. The 

 gap is flanked with bushes of miki miki and young Pandanus. On Plate 

 80 are shown a number of miki miki bushes growing close to the beach of 

 the lagoon. The east face of Manga Reva Island is seen across the channel 

 with Mount Duff in the rear (see also PI. 79). A view of the lagoon coral 

 sandy beach seen at low tide is given in Plate 81. The bushes extend to 

 high-water mark, and are frequently, as well as the Pandanus, washed by 

 high tides (PI. 89, figs. /, a), and often run close to the sea face when the 

 islets are narrow (PI. 91, figs, 1, 2). On the lagoon side we find, occasionally, 

 stretches of l^cach rock (PI. 89, fig 2). On the sea face the vegetation runs 

 along the ridge of the coral rubble dam (Pis. 79, 83-85, 87, 88, 90, fig. 4 



Where the islets ai'c narrow (PI. 91), coral rubble often extends across the 

 islets from the sea face to the lagoon side or runs along the flanks of the 

 gaps from the sea face towards the lagoon beach (PI. 90, fig. i). Some of 

 the wider gaps are shut off from the lagoon by sand dams, the extensions 

 of the adjohiing lagoon beaches across the head of the gaps (PI. 79), as 

 seen from the coral rubble flat. A view of a lagoon sand dam taken from 

 a point nearer the lagoon dam is seen in Plate 82 and in Plate 90, fig. 1. 



Some of' the wider and deeper gaps cut through the coral rubble flats 

 (Pis. 79, 83), and extend well across towards the lagoon.^ I did not notice 

 any sand dams across gaps, on the sea face, as is so common in other reefs 

 of the Pacific. 



The mode of formation of the coral rubble beach is well shown on 

 Plates 83-87, 90, fig. 2. In Plate 84 the outer reef flat is covered by the 

 tide, and washes at the base of the rubble beach the larger pitted and 

 honey-combed horses which indicate the former level of the reef flat before 

 it had been planed down by the sea and the material thrown up to form 

 the shingle, and rubble beach dam (PI. 84). The Nullipore knolls on the 

 sea face of the reef flats do not assume at Manga Reva the prominence they 

 have in other reefs of the Central Pacific. 



In Plate 85 is a similar view of the reef flats and rubble dam seen looking 

 south at a somewhat lower stage of tide and with larger coral horses thrown 

 up at the base of the rubble beach or still forming a part of the reef flat. 



' Dr. Seurat (fttablissemcnts fian^ais de rOct-anie, gouvernement dc T:ihiti : L. G. Seurat, Obser- 

 vations sur les iles basses de I'archipel des Gambier, Mai 1903, p. 2.) has called attention to this 

 structure in the islands on the encircling reef of Manga Reva. 



