82 bulletin: museum of comparative zoology. 



the atolls or islands encircled by recent coral reefs beyond forming the 

 substratum upon which the recent corals have grown and established 

 themselves as a comparatively thin crust. 



The underlying limestones have performed exactly the same part as 

 the volcanic substratum in other islands of Fiji, such as Totoya, Kim- 

 bombo, Wakaya, Makongai, Moala, Nairai, Ngau, and others. In both 

 cases the platform upon the edge of which the corals grow has been 

 prepared by extensive submarine erosion, dating from the time when the 

 limestones were elevated by the volcanic rocks which crop out everywhere 

 in Fiji, — an elevation which was not necessarily synchronous throughout 

 Fiji and may have taken place at several distinct periods, so as to make 

 it often difficult to determine the relative age of the limestones and of 

 the volcanic masses. 



Professor David, of the University of Sydney, has been kind enough to 

 assist me in obtaining the services of one of his students, Mr. E. C. 

 Andrews, to collect fossils from the elevated limestones of Fiji. Mr. 

 Andrews has spent a part of the summer in Fiji, collecting material and 

 exploring in detail some of the faces and slopes of the elevated reefs of 

 the Archipelago, and has obtained ample material to determine the age 

 of these elevated limestones. 



In the earlier discussions of the thickness of recent coral reefs by 

 Darwin and Dana, no attention was paid to the possibility of the sub- 

 stratum of recent reefs consisting of tertiary limestones. Elevated lime- 

 stones containing corals of tertiary age were considered as of recent 

 origin and as pointing to a great thickness of modern reefs. It has 

 been shown in Florida that the modern reef is not more than about 

 50 feet thick, and is, according to the borings from the artesian well at 

 Key West, succeeded by tertiary limestones, in which corals occur at 

 intervals to a depth of 2,000 feet. 



It has been stated by Dana and others that the borings from the 

 ai'tesiau wells at Honolulu, to the rear of the shore line of the fringing 

 reef of Oahu, indicate a great thickness of modei'n reef corals. These 

 statements are based upon the examination of samples of finely ground 

 particles of limestone accompanied by an occasional fragment of coral, 

 the age of which has not been determined. The statements are furtlier 

 supported by the evidence of Mr. J. A. McCandless, the engineer in 

 charge of the boring, who asserted to both Mr. Dana and myself that in 

 boring all his wells the tool passed through a great thickness of corals, at 

 various levels. During my recent visit at Honolulu, I was so fortunate as 

 to be on the spot where Mr. McCandless was boring a ten-inch well, about 



