118 BULLETIN: MUSEUM OF COMPAEATIVE ZOOLOGY. 



The coral patches now thriving on the slopes of the reef are growing 

 on the slopes of the former elevated reef, which from its disintegration 

 has formed the extensive reef flats covered with dead corals and flanked 

 with negro heads. 1 The patches of living coral and the heads do not 

 extend to a greater depth than six to seven fathoms. Nowhere at ten 

 fathoms have we found any isolated heads ; the bottom at that depth 

 near a coral reef being invariably clean coral sand, with fragments of dead 

 coral. A similar bottom extended into deeper water, and characterized 

 the coral sand lanes separating the coral heads. So that the present reef 

 corals may be said in the upper part of the reef to form a crust over the 



1 I cannot forbear quoting Jukes again at length (Voyage of the "Fly," Vol. I. 

 pp. 340, 341) regarding the negro heads, to show how accurately he noted the existing 

 state of things on one of the great reef fiats we have just described. Jukes, in 

 fact, all but named the existence of a former elevated reef as the source from which 

 the negro heads were derived. He writes : " On a reef, forming part of the Great 

 Barrier, about twelve miles southwest of Raine's Islet, I observed a very remark- 

 able, and as far as I know unique fact, which seems to favor the idea of the reef 

 having been slightly elevated in that locality. The mass of reef alluded to is two 

 or three miles long, and from a quarter to half a mile in width. Near its southern 

 extremity, and about fifty yards from its inner edge, there is a range of large coral 

 blocks permanently above water. Immediately to the south of them is a gap or 

 channel of deep water, about a quarter of a mile wide, to the south of which another 

 reef sets on. These blocks are full two hundred yards from the outer edge of the 

 reef, and protected by it from heavy breakers, and it is only at high water that the 

 last curl of surf reaches thern through the gap to the southward. No conceivable 

 storm could lift them into their present condition, with the reef around having its 

 present extension. They not only rested on the reef, but appeared to pass down- 

 wards into it, as if forming part of its mass. They were composed wholly of a 

 species of Porites, very solid and massive, with comparatively small cells. They 

 seemed to be in the position of growth, with the cells all pointing upwards. The 

 blocks were often as much as twenty or twenty-five feet in length* and rose from 

 the reef to a height of ten or twelve feet ; they were very rugged, and apparently 

 much worn, the cells being apparent at the surface in the more sheltered hollows 

 only of the masses. They ran along a line parallel to the inner edge of the reef, 

 for three or four hundred yards. High-water mark was very apparent on them, 

 forming a horizontal line, below which they were much smoother than above it. 

 They ended upwards in sharp points and crags, much honeycombed and excessively 

 rugged. From high-water mark to some of their summits was about eight feet 

 and a sufficiently large mass of them was visible at high water to show like a line 

 of large black rooks, at a distance of two miles. I examined them attentively, and 

 walked about them at low water, and could form no other conjecture respecting 

 them than that they had been produced under water, and raised above it by the 

 elevation of the mass on which they reposed. They looked exactly like the rem- 

 nants of a much larger mass that had been gradually eaten away and destroyed by 

 the action of the sea and weather." 



