AGASSIZ: FIJI ISLANDS AXD COEAL REEFS. 59 



The little bay was studded with mushroom-shaped and conical islets 

 and rocks, all deeply undercut (Plates 91, 93), and the bottom in from 

 two to four fathoms was covered with sunken coral patches and heads 

 rising at all depths. 



Some of the islets were covered with bushes and cocoanut trees, like 

 the main island. The highest point of oS^avutuiloma is 210 feet; it is a 

 little over one mile in length, and is larger than Navutuira. The shape 

 of the outer reef flats enclosing the lagoon of Yangasa (Plate 22) is ir- 

 regularly rectangular, with rounded angles ; the faces are each about 

 five miles long, the western face being the longer. On the eastern and 

 northeastern side, the reef flat is quite narrow, but it is studded along 

 the inner edge with a belt of heads and coral patches and negro-heads. 

 Ofl" the southeastern horn, the reef flat becomes very wide, projecting in 

 a point fully two miles beyond its general line. The reef flats of the 

 southern and western faces are also broad, fully a mile in width in some 

 places, and at the northwestern horn the reef flat is more than a mile 

 and a quarter wide. 



On the northern face of the lagoon a tongue of deep water (l-to fath- 

 oms) fully a mile wide runs towards the centre of the lagoon ; this is the 

 passage used for entering the lagoon. The slope of this part of the lagoon 

 is very steep, and it is studded with coral patches and heads growing 

 upon the remnants of the former island of Yangasa. This narrow and 

 deep tongue of the ocean represents probably an original valley formed 

 in the uplifting of the island, and has no connection with a subsidence 

 of the island during the formation of the encircling reef, which has 

 grown subsequently upon the platform of submarine erosion formed by 

 the wearing away of the original land mass. The average depth of the 

 northern part of the lagoon is from 14 to 19 fathoms. The southern 

 part, between Yangasa Levu and Navutuiloma and the reef flat, is shal- 

 lower, from six to twelve fathoms, with a still shallower belt along the 

 inner edge of the southern reef flat. 



Off" the southeastern extremity of Xavutuiloraa extend a number of 

 mushroom-shaped rocks and islets, deeply undercut and eroded into fan- 

 tastic crests, pinnacles, and summits. The reef flat of the western face 

 of the Yangasji lagoon is full of thriving coral patches, which extend 

 along the inner edge, between and upon the negro-heads, down to seven 

 or eight fathoms. The formation, by erosion and denudation, of diminu- 

 tive or incipient sounds, as in the bay of Navutuiloma, is interesting as 

 representing one stage in the action of such processes, of which others 

 can be followed in the conditions which have been reached by such 



