128 BULLETIN : MUSEUM OF COMPAEATIVE ZOOLOGY. 



reef, its character is similar to that of Viti Levu, the substratum of 

 the reef flats being either hard volcanic rocks, or stratified Tolcanic 

 mud, or remnants of elevated limestone. The northern shore of Yanua 

 Levu from Cape Undu (Plate 4) west is flanked by wide extensive 

 stretches of barrier reef patches ; between them and the shore exists a 

 broad navigable channel full of islands and islets, and the whole of the 

 shore is also indented by deep bays separated by prominent promontories 

 almost isolated from the larger island ; plainly indicating that the flats 

 and patches occupy areas formerly covered by large islands or by former 

 slopes of spurs from Vanua Levu itself, which have been eroded and de- 

 nuded and separated from the larger island. The outer flats and patches 

 of the barrier reef, which as it extends westward beyond the Mali Pas- 

 sage forms the Great Sea Eeef, and is nearh" thirty miles distant off" the 

 western point of Vanua Levu. The islands and islets off the north coast 

 of Vanua Levu form a broad belt of islands separated by islets, rocks, 

 and patches ; on the western extremity of the belt is Yendua Island and 

 the islets extending westward. 



The existence of fringing reefs inside of barrier reefs is a very strik- 

 ing feature of the Fiji coral islands. Their absence in some localities 

 has been explained by Dana ^ on the supposition that the conditions 

 are more favorable to the growth of corals on a barrier than on an 

 interior fringing reef. Yet in some of the wide lagoons of Fiji the 

 corals of the fringing reef grow quite as luxuriantly and to the same 

 depth as those on the outer edge of the barrier reef, and are often 

 more abundant than those of the lagoon slope of the barrier reef. 

 Depths of five to six or seven fathoms are those of the most vigorous 

 growth of corals on the outer face of such barrier reefs or encircling reefs 

 as I have examined in Fiji, a depth corresponding to that observed in 

 the Bahamas in similar positions. 



Some of the reefs on the northwestern face of Vanua Levu (Plate 4) 

 apparently illustrate admirably the foi'mation by denudation and erosion 

 of small reef flats awash, and of reef flats destitute of islands or with 

 islands encircling a shallow lagoon. It will be noticed that these flats 

 and pseudo atolls rise from a comparatively shallow platform, — nine to 

 twenty fathoms, — and evidently represent the different stages of denu- 

 dation and of erosion of islands which have been left on one side of 'the 

 reef flat, or have disappeai-ed, leaving an irregular enclosing reef, or have 



beach along Savu Savu, as well as Waikava and the adjacent islands, consists of 

 coral upheaved to a height of thirty feet. 

 ^ Corals and Coral Islands, pp. 138, 278. 



