158 TROF. W. J. DAKIN : EXPEDITION TO THE 



or lagoonlets. The water of the lakes is salt, and often disappears altogether 

 at low tide. In other cases it is permanently present, and deep, but rises and 

 falls with the tide outside. One in Long Island is only a few yards across, the 

 banks are of coral conglomerate and loose blocks, and the floor of the lake or 

 lagoonlet of coral with a deposit of mud. We shall refer in greater detail to 

 the formation of these lakes when describing the same on the islets of the 

 Easter Group. 



Mention must be made here of the channel to the east of Long Island. It 

 is very much used by fishing boats passing north and south, for it has a 

 depth of 20 fathoms, and that quite close to Long Island itself. The channel 

 seems to have broken through the reef, cutting off Morning Reef to the east 

 of it from the coral masses on the west. Perhaps Long Island itself owes 

 its formation to the development of this channel. As one would expect from 

 the depth, a strong scour runs through the channel which bears every 

 appearance of erosion. We dredged several times here and with excellent 

 results. 



Nothing more remains to be said about the reefs except that coral growth 

 is active at the present time in the lagoons wherever the water appears to be 

 free from mud. To the north-west of the coral marked Noon Reef on the 

 chart is an expanse of water almost completely surrounded by coral reef. 

 It can be entered bj r a channel to the west of Long Island, and by another 

 one to the S.W. indicated by the arrow on the map, text-fig. 2, p. 136. This 

 expanse of water is called " The Lagoon " by the fishermen (no other area is 

 spoken of as lagoon by the fishermen anywhere in the Abrolhos Group). 

 Depths of 6-12 fathoms occur, and the bottom is almost everywhere of 

 coral. We investigated this area with the motor dinghy on many occasions, 

 and were always delighted with the gorgeous growths of coral seen 

 perfectly through the clear water. The most abundant coral is a species 

 of Madrepora with a most beautiful blue-purple colour. This occurs 

 everywhere, rising from the bottom in the form of great " shrubs." The 

 more compact corals like Meandrina and Astrcea, etc., do not seem to 

 flourish here. Pocillopora is common in places. We have never obtained a 

 Fungia at any of the Abrolhos Islands, and have seen no traces of such, not 

 even fragments. Several times we tried the dredge in these lagoons and 

 pulled it forcibly over the bottom, tearing away the more delicate corals 

 at the risk of losing the dredge and cable, but we never obtained anything 

 but coral and the small Crustacea and worms which live in the crevices. 



It would seem to us that the outer margins of the coral reefs fringing the 

 Wallaby Group are extending seawards by active coral growth, at least in 

 places, but that such growth is very slow. In the lagoons we see coral growth 

 in certain areas, and sandy deposits with no coral growth in other parts. 

 Here active solution and erosion is taking place, whilst there we find 

 that coral growths are forming, or coral fragments are being heaped up by 



