THE ATOLL OF MINIKOI. 47 



Indeed with a short crowbar the presence of such a reef is indicated often for 30 to 40 

 yards, and it would appear to underlie a not inconsiderable part of the sand-flat. Attached 

 organisms, other than those which have been already mentioned, are rare in this outer 

 area, but nearly all the free forms of the boulder zone with the exception of Ophiurids 

 are found in as great, or even greater abundance. The black beche-de-mer is extremely 

 numerous, and myriads of small fish dart between the branches of the corals. Annelids and 

 Sipunculids are rare, but generally free life on the coral reefs of the deep sea is nowhere 

 as abundant nor varied as on tropical continental coasts, or on even moderately rich gi-ound 

 of the Mediterranean and English seas. 



The rest of the sand-flat is nearly bare of all organic growth. Opposite Minikoi island 

 two small green algae are found in patches, and here and there clumps of a finely branch- 

 ing nuUipore grow, nearly imbedded in sand. Surface-living Holothurians are very common 

 in places, and a small species of Ptycliodera occurs locally under the weed in great abund- 

 ance. Living in the sand are large numbers of a white Holothurian, a large Sipunculid 

 and two Synapta, besides vast numbers of smaller species of the same groups. In addition 

 heaps of sand, 4 to 5 inches high, in a calm sea stud the whole, the castings of an 

 immense Enteropneust, the end of the body of which is often li inches in diameter 

 when distended with sand. 



The sand ends about 100 yards outside the line, marked 2 fathoms in the chart, 

 opposite and to the north of Minikoi island, the intermediate area generally being covered 

 with coral shoals, intersected by channels with about 2 fathoms of water. These shoals 

 are usually flat on the top, bare or hollowed out in the centre, with perpendicular, or 

 overhanging sides — especially towards the deeper part of the lagoon — covered with coral 

 growth. On their summits the chief coral is Porites arevosa, but all the previously 

 mentioned lagoon genera are represented ; massive Astraeids tend to be the dominant forms 

 on the sides. All are much infested with boring organisms, Lithodomus, Cirripedes and a 

 Gastropod as well as the usual Sipunculids and Polychaets. The patches decrease in size 

 towards the sand area, on which they seem on the whole to be encroaching. To the south- 

 west and north of the atoll coral patches may occur near the edge of the sand-flat, but 

 there is no definite broad line. This is especially the case by the boat channels and 

 northern passage. By the side of the latter I found what appeared to be the remains of 

 a patch, which for some cause or other had been killed the previous year. It was a round 

 mass, standing in 3 fathoms with 1 foot of water covering it at low tide, sides precipitous, 

 diameter about 18 yards. Its surface was rotten, its sides extremely sparsely covered with 

 living corals — the greater part dead at the base— with much dead and rotting coral. Four 

 other patches seemed to be in the same condition, but they had a certain amount of 

 weed, and would appear to have been killed some time previously. Several other reefs in 

 the vicinity had also been affected, but none to the same extent; some, however, had had 

 in places quite sensible slips at the sides. Free animal life on all the shoals, it may be 

 noted, is extremely scarce. 



The slope from 2 or 2^ fathoms, the general depth of the edge of the surrounding 

 flat and reef, to the deepest waters of the lagoon is gradual and regular. Coral patches 

 occur everywhere but much more sparingly in the deeper waters and towards the north ; 

 indeed the centre of the lagoon is fairly clear. The patches all reach within a couple of 

 feet of the surface. With the lead I failed to find any incipient patches, and I lined 



