42 



J. STANLEY GARDINER. 



a marked line, and the fissures are small, many closed over by nullipores, which may 

 perhaps leave small blowholes. 



The reef between the last two positions described gradually varies from the one to 

 the other. In one place for about 200 yards the whole of the seaward face of the but- 

 tresses and for some distance up the channels is singular in being absolutely covered over 

 by a yellow zoanthid actinian. Off Wiringili and Ragandi islands the reef is nearly the 

 same as off Teveratu point, but the conglomerate zone is broader, more marked, and very 

 rugged (Fig. 10). Between Wiringili and Minikoi the reef outside the boulder zone is 



Fig. 10. Seaward beach of Wiringili with masses of conglomerate. {From a photograph.) 



intermediate between the reef off the end of the large island and the reef of the whole 

 of the west and north sides of the atoll. The latter does not differ materially in different 

 parts, and the description in one position will serve for the whole. 



In a cross section between Wiringili and Ragandi three zones are well defined, the 

 fissure, reef-flat, and boulder. The fissure zone does not very materially differ from that off 

 the end of Minikoi island, but its edge against the sea is more irregular, some masses 

 dropping with a cliff to two or three fathoms, others tailing off gradually. It varies in 

 breadth up to 30 yards, and slopes about two feet in this distance from its crest ; the 

 latter is a slightly higher part just e.x posed at low springs, six or eight yards across. Further 

 outside the slope quickly attains a depth of four or five fathoms, slowly increasing for some 

 distance. The bottom is fairly smooth, covered with spreading nullipores and studded with 

 round masses of the same and coral colonies, the former always with a coral core. There 

 is no appearance of the great masses found off the reef to the south of Miuikoi island. 

 The seas break just outside the edge of the zone, which except the crest is swept by the 

 waves in all weather. The fissures seldom have overhanging sides, or any accumulation of 

 coral blocks or sand in their channels. They generally start in the crest and slope to 

 about 2^ fathoms outside ; few reach through to the reef-flat, from which at low tide the 

 water cannot readily escape seaward. The water at low tide rushes up the fissures and 

 a certain amount wells over on to the reef-flat, though most, being thrown back by the 

 crest, escapes with great force down the channels. The buttresses are pitted on the surface 

 into small rounded hollows, which are often filled with algae, allied_ to Halinieda, or with 

 small coral colonies, mostly branching facies of the usual genera. Generally, however, the 

 hollows are empty, the rock beneath merely covered with a nullipore, or a flat green alga 

 of some sort. If the surface be broken, a nucleus, usually of coral, is reached after several 

 inches of a light concretion of worm tubes and Lithothamniuii. The walls and floors of the 



