218 "ALBATROSS" TROPICAL PACIFIC EXPEDITION. 



The Heliopora reef, described by Sollas as occupying the floor of Taiisale,^ 

 exists under conditions very simihir to those of extensive Porites and Mille- 

 pora reefs, which I shall liave occasion to refer to in my description of 

 some of the Gilbert and Marshall Islands, more especially when giving an 

 account of the Millepora and Porites reefs of Taritari. 



The surface rock of the land rim of Funafuti consists of innumerable 

 small fragments of coral and of coral breccia, more or less decomposed into 

 soil. On the lagoon side, on the north end of the island of Funafuti, 

 nothing but reaches of coral breccia, more or less disintegrated, could be 

 seen, with short stretches of coral sand beaches separating them. South of 

 the monument of Funafuti there is an extensive dry sink in the centre of 

 the island. This is the southern extension of the same sink which one 

 crosses going from the village to the bore. 



Dr. Mayer examined the coral breccia, the beach rock, and the con- 

 glomerate existing towards the southern point of Funafuti Island, where 

 a line of low coral breccia cliffs and an extensive coral sand beach ter- 

 minates to the south against steep buttresses, and alternates with ridges of 

 coral breccia. He found on the lagoon side a conglomerate composed of 

 rounded water-worn masses of hard crystalline limestone, cemented together 

 with fragments of shell and of sand. This rock extends only about one 

 foot above high-water level, and to the eastward or inland, back of the 

 beach, one finds a mass of coral heads, and more or less rounded masses of a 

 somewhat crystalline structure. These masses and fragments of coral rock 

 or shingle are not cemented together, but plainly show that they are derived 

 from tlie disintegration of the adjoining crystalline limestone masses of coral 

 conglomerate, of which only a few outliers are left intact. As at other points 

 of Funafuti, these outliers of beach rock, of coral breccia and conglomerate 

 are, on the lagoon side, separated by long stretches of fine coral sand 

 beaches, while on the sea face of the southern part of the island, as else- 

 where in Funafuti, we found but little coral sand, the steep beach being 

 composed almost entirely of broken fragments of crystalline limestone, many 

 of them water-worn and rounded as on the lagoon side, but most of them 

 are large masses of jagged rock, evidently thrown up by unusually powerful 



' Page 510, fig., Proc. R. S., February, 1897. 



