DESCETPTION OF SMALL INLANDS OF THE ATOLl . 91 



of the becach. S.E. of the island a pi'ojcction of the platform into the lagotni for scvci'al hundred yards 

 protects it in that direction. 



At tho base of this islet and rcstino- on the or^ean platform is a thin sheet of breccia -which contiinies 

 around the S.W. and north of the islet, covering the platform, but ■worn to a rugged outline by the 

 action of the waves. Resting unconformably on the inner edge of this are a series of more or less 

 indurated fine and coarse sand.stones (L.3. and L.2.A.) and finer breccias (L.2.B.), dipping N.E. towards 

 the island and the lagoon at an angle of 5" to 8". The finer breccias (L.2.B.) are alst) exposed at the 

 S.E. corner on the lagoon side of the islet, irnder which it appears to extend. Beyond these sandstones, 

 seawards, and projecting upwards through the older breccia, are large and small bosses of Porifes, a few 

 of which corals have been noted at the last islet, and were seen, though rarely, on the platform between 

 that islet and this. Here, however, they have suddenly become much more numerous, while to the 

 S.W. they are abundant, though smaller than those seen at Fiiagea, averaging here 2 to 3 feet in diameter 

 by 1 to 3 feet in height above the platform and breccia, some being nearly or quite up to high-water 

 level. They are bounded on the ocean side by the corrosion zone, and become less numerous immediately 

 to the south of the islet. Here either a sjjace remained as a channel, which we think probable, during 

 the growth of the Porifc.t and the subsec|uent breccia deposition, or both the Pi5;77''.s and breccia have 

 been subsequently eroded. 



The position of Tefala on the reef is much nearer the ocean margin than any islet on the western 

 reef between this one and the northern one of Te Afualiku, over 10 miles distant, and the undoubted 

 cause of this diflerence is the protection Tefala receives from the presence of the remains of the breccia 

 sheet and of the Forifes bosses, together with the more or less indurated coarse and fine sandstones and 

 newer breccia on its western side, The persistence of the older breccia here is due to the great number 

 of the bosses of Pontes, which is the most enduring of the coral masses found on these islets. Useful 

 as it is, the protection afforded to the islet is not, however, equal to what it once was before the breccia 

 was corroded and denuded, and from this it would appear that the Pontes and older breccia must have 

 supplied first a base for an island, and now a good protection to a later stage of its existence since it 

 has been shifted nearer to the lagoon. This transference of material from one position to another is 

 shown by (1) the dip of the sandstones, and (2) the fact that those now nearest in to the beach on the 

 ocean -side of the islet, but dipping mider it, are, in one or two places where they have been recently 

 uncovered, higher than those further seawards, although they are softer than the latter. From the 

 contour of the breccia and the general strike of the sandstones, it would seem probable that the latter 

 were laid down in and sheltered by a small bay on the lagoon side of the earlier islet. We must, 

 therefore, reasonably infer that the islet is still moving lagoonwards, as, indeed, is inevitable from the 

 gradual erosion of elevated obstructions on the platform. 



On this islet the descending order, chronologically, of deposition of the several formations appears 

 to be : — 



10. L.9.B. and 0.4. 



9. L.8.A. Eecent, but not covered with vegetation. 



8. L.7.B. Older, sandy and loamy soil. 



7. L.6. Sandy and loamy soil. 



6. L.3. Newer Lithothamnion sandstone. 



5. L.2.B. Newer reef breccia. 



4. L.2.A. Old lagoon conglomerate sandstone. 



3. L.3. NuUipore sandstone. 



2. O.2.E. Breccia sheet. 



1. Pontes and 0.3. Dead reef, now forming the reef platform, probably O.L.I. 

 The history of this island, indicated by the order and position of its deposits, is as follows : — On the 

 platform, over and including the present breccia remains, existed a breccia sheet of siniihir height to 



X 2 



