THE ATOLL OF MINIKOI. 43 



fissures are usually smooth, and encrusted completely with nuUipores. Free animal life of 

 any sort is rare ; a few thick -spined Echinoids and large crabs wedge themselves into the 

 hollows ; brilliantly coloured fish wash to and fro with the waves in the fissures ; between 

 the branches of corals and weed a few Alphaeids find a refuge with an occasional Cyprid 

 and Strom b. The crest of the zone is not always present in such a marked manner, though 

 an inner part, densely covered with green algae, in which the fissures mostly end, can 

 always be distinguished. Its surface has the regular worm tube and nullipore structure, only 

 in greater thickness ; corals are rare, a few mammillated nullipores being the only calcareous 

 organisms. 



The reef-fiat is about 50 yards in breadth, presenting almost the same characters as 

 in the last position described. The greater part of its surface, being situated about 6 inches 

 below the crest of the outer zone, is at any state of the tide covered with water, in which 

 there must be some change through the fissures. Its surface is absolutely free from loose 

 coral boulders, and is for the greater part bare save for low algal growths. It is clean, with 

 no dirty appearance from mud or sand, and, if broken into, is seen to be formed of hard coral 

 rock. Small incrustations of nullipores are found, but they are never of any real import- 

 ance, nor can they in any way affect the general height of the whole. The same genera 

 of corals grow as are found on the fissure zone ; spreading forms of Montipora alone attain 

 any size, their colonies sometimes covering 2 or 3 square yards. The mo.st abundant genus 

 is PociUopora, of which two forms, finely and coarsely branching, are numerous ; Coeloria 

 daedulea also is of considerable importance. Corals attract the eye, and hence tend to 

 assume an undue signification. It is very unusual for them to cover more than 10 per cent, 

 of the surface of any reef, sufficient for wastage, but not enough to alter the general level. 

 Towards the exterior masses of hard rock, 2 to 3 feet high, are found irregularly about 

 every 40 yards. They are pitted on the surface and rotten, perhaps the outside a mass of 

 worm tubes, surrounding a solid rock core. Although I passed along this reef in the be- 

 ginning of September, 1899, after very heavy south-west gales, I failed to find any large 

 masses thrown up by the seas (negro-heads), nor did I ever find any rocks on the fiat in 

 process of cementation on to the reef. Blocks added thus usually can be easily split off 

 with chisels along the line of cementation, but I failed to break any of these. / am hence 

 driven to the concltision that these masses are true pinnacles, that they once absolutely were 

 part of the reef itself and were left, while the rest was completely washed away. Of free 

 animal life, other than that found on the fissure zone, Holothurians alone are prominent. 



Of these two zones as far as the north passage into the atoll little further need be 

 said. They have nearly the same characteristics, but the fissure zone increasingly becomes 

 more broken and less defined at its outer edge, which tails off very generally by simdar 

 masses to the seaward depths. The crest is in many parts absent, and the two zones merge 

 into one another; pinnacles are scarcer. In three places between Ragandi and the passage 

 the reef is lower, forming boat channels, which are used above half-tide in the north-east 

 monsoon. These passages are merely extra large fissures, which run further into the reef- 

 flat; they are kept open mainly by the scour of the tide, preventing coral and other 

 calcareous growths. 



The boulder zone (Fig. 11) is an area of rough blocks of rock, separating the reef-flat 

 from the lagoon. It is about 30 yards broad, moderately sharply defined on both sides; 



(J— 2 



