128 MR. A. E. FINCKH. 



The edge of the reef platform on the ocean side traced landwards up to the wash of 

 the waves at low- water spring tides is covered with the lichenous Lithoihamnion, 

 which here, as in the lagoon, presents the appearance of having had its growth 

 impeded. Both the thinly-branching and the knobby Lithoihamnion are totally 

 absent. 



The following is a detailed description of this eastern rim of the atoll near the main 

 diamond-drill bore. The lagoon platform here is about 165 yards in width. At the end 

 it drops in places perpendicularly into from 2 to 3 fathoms of water, in others it forms a 

 slope, but this is always steep. The bottom below is almost pure Halimeda sand. 

 The platform has been formed, as it appears, by the transformation of large expanses of 

 Heliopora cccrulea into reef rock by the process already mentioned. The dead 

 Heliopora is seen everywhere in situ, though in most places its presence is obscured 

 by the remains of its conqueror the Litliothaninion. The whole has a decidedly 

 barren-looking aspect. At low- water spring tide the platform is left dry, with the 

 exception of several shallow pools, the sandy bottoms of which are about 6 inches 

 below low water. Some of these pools proved to be lying in hollows belonging to 

 holes in the reef platform which were once of considerable size, but which subsequently 

 have been filled up with sand. An iron rod could be pushed down some 5 feet before 

 meeting with an obstacle. The surface platform harbours innumerable Ophiuroidea, 

 numbers of molluscs and sponges, but scarcely any coral or Halimeda. The last two 

 occur only in the reef pools, so that they are never completely uncovered by water. 

 The mode of growth of the coral, which was only represented by Pontes li.mosa, offers 

 many features of interest. A description of these is given in the Sub-section on the 

 mode of occurrence of the chief reef- forming organisms (p. 137). 



JlaJimeda grows very abundantly in sandy patches of the platform ; it occurs, too, 

 in large I'oundish masses on the edge of the reef platform, and the submarine wall of 

 tlie platform is also covered with it. In the latter position here and there minute 

 coralla of PociJlopura paiicistellata are met with. On the whole the absence of any- 

 thing like the vigorous growth so characteristic of the western rim, both on ocean and 

 lagoon face, is very striking. The apparent absence, too, of the lichenous Lit hath amnion, 

 together with the total disappearance of the branching and knobby forms of this 

 calcareous seaweed, is very noticeable. 



We now leave the lagoon platform by ascending the sandy beach : the island here, 

 where it has to be crossed in order to reach the ocean platform, is about 200 yards 

 wide. Standing on the Hurricane Bank, we have lying at our feet the ocean platform 

 300 feet wide, consisting of typical Litkotluimnion rock. This platform, like the 

 lagoon one, is characterised by its barrenness, but differs from the latter by being- 

 divided into conspicuous zones (see plan on Plate 17). The first two of these, the 

 erosion and the corrosion zones, which are totally dry at most low tides, are devoid 

 of life. At about 78 feet out towards the ocean from tne foot of the Hurricane Bank 

 the first growth is met with in the shape of non- calcareous seaweed of an inconspicuous 



