AGASSIZ: FIJI ISLANDS AND CORAL EEEFS. 35 



atolls in Fiji. We must remember, however, that the formation of such 

 atolls may also be accounted for as the result of the denudation and sub- 

 marine erosion of a [)atch of elevated limestone, cut first into a sound, and 

 then, with the disappearance of the outer rim, into a lagoon surrounded 

 by a shallow reef flat ; or the same result may be accomplished from the 

 wearing away of islets of volcanic origin enclosed within the outer reef, as, 

 for instance, from the disintegration of the islets now left in such atolls as 

 the Kimbombo Islands, Komo, and others, or of islets consisting of 

 elevated limestone like the Aiwa Islands, Katavanga, Yekai, and others. 

 The structure of the negro-heads occurring upon the outer reef flats, or 

 their position near either a volcanic or an elevated reef region being the 

 only guide as to the category to which belong such atolls as Thakau 

 Mata Thuthu, Thakau Vutho Vutho, the Adolphus Eeef, Dibble's, Duff, 

 and Bell Reefs, Thakau Tambu, Malevuvu, etc. 



Such a cluster as Budd Eeef suggests an explanation for the for- 

 mation of interior atolls, like those described by Darwin as occurring 

 in the Maldive Islands, very different from the one suggested by him. 

 Were Thombia cut down by erosion to the water's edge or below, and 

 changed into a small atoll, we should have a secondary atoll within the 

 area enclosed by Budd Eeef, and were the other small islands of the 

 cluster summits of elevated limestone, and should they in their turn be 

 cut down, they might form in such a large lagoon as that of Budd Eeef 

 other diminutive atolls, or small atolls enclosed within an atoll. Such 

 interior atolls, if my view of the formation of atolls is correct, could only 

 be formed in lagoons of considerable depth and size, so that the seas 

 formed by the prevailing winds should have a long sweep and rise to a 

 considerable height, and thus possess great disintegrating power. I shall 

 refer again, when describing Vanua Mbalavu, to the probable origin of 

 such great depths as foi'ty-seven fathoms inside of the reef encircling the 

 islands of Budd Eeef. 



Komo. 



Plates 19*, Figs. 9-11, and Plates 32, 63-65. 



Komo Island is a narrow ridge of volcanic origin, about a mile and a 

 half in length, rising to over two hundred feet. Its western extremity is 

 connected by a coral reef full of volcanic negro heads, two of which are 

 mushi-oom-shaped and of considerable size, with the islet of Komo Ndriti, 

 itself about seventy feet high. Komo lies in the southeastern horn of the 

 lagoon (Plate 22) close to the southern face of the outer reef flat, from 



