398 PROCEEDINGS OP SECTION C. 



which determined the present Barrier Reef dates from Pleistocene times, 

 and was followed by a modern very slight uplift. 



An island named Masthead, near the southern extremity of the 

 Barrier, was searched in 1904 by a scientific party organised by one of 

 us. A description of this island and part of its fauna has appeared 

 '(Hedley, Proc. Linn. Soc, N.S.W., xxxi., 1906, pp. 453-479, &c.). 



Material for the present article was gathered by us in 1906 during 

 a visit to the reefs near Cooktown. We are enabled to present definite 

 traverses across three reefs in various and progressive stages of growth, 

 showing the superficial geological structure and distribution of life 

 along actual sectional lines. The ecology of coral reefs has been so 

 little studied that we would draw attention to an interesting series of 

 articles on the fauna of the Djibouti reefs in the Red Sea, by Professor 

 H. Coutiere (Bull, du Museum, Paris, iv., 1898, pp. 38, 87, 155, 195, 238, 

 274). 



II. {a) TRAVERSE— HOPE ISLAND REEF. 



The Hope Islands were so called by Captain Cook, after the wreck 

 of the Endeavour, because here he first took hope that he might save 

 his ship and the lives of his company. A view of the reef flat at Hope 

 Island is given bv Mr. W. H. D. Le Souef {" Wild Life in Australia," 1907, 

 p. 347). 



Details of the traverse from north to south across the reef serve 

 to show definitely the distribution of organic and inorganic structures 

 on a typical reef integer of the Great Barrier Reef (see Plates I., II.). 

 A cursory examination reveals the fact that the fauna of the coral reef 

 — which is covered at every tide — mainly consists of various other 

 families than the Madreporaria or true (stony) corals. Each of the 

 three traverses was about a mile long, and it is interesting to note that 

 the solid growth of living coral formed a fringe constituting some 20ft. 

 or 30ft. at each end of the total of 5,000ft. or 6,000ft. representing the 

 whole width of the reef. 



Starting at the north edge of the reef (the leeward for the greater 

 part of the year), at low spring tides the living rampart of dense massive 

 corals such as Goniastrea and Pontes project slightly above water for 

 about an hour each day of such tides. This rampart is well defined all 

 round the reefs, but is notched by channels some 4ft. deep (reaching 

 to the foot of the rampart), in which more delicate branching madrepores 

 and millepores flourish. The latter are being constantly broken off on 

 the windward side, and driven up and over the edge of the reef, con- 

 stituting, as we shall see, the " clinker embankment." 



Within the rampart, and level with its cap, are to be found more 

 accessible corals, forming a second zone about .30ft. wide. Here occur 

 Turbinaria, Coeloria, Fungia, Galaxea, Herpetolithes, and many madre- 

 pores which, while not so delicate as those living at the foot of the huge 

 blocks of Pontes, &c., are too frail to withstand the full force of the 

 surf. Here also occur many Tridacnas (clams) — the larger free, while 

 the smaller are buried mouth uppermost in coral masses. 



