226 Reviews — The Atoll of Funafuti. 



they are equally as abundant in the cores and loose materials 

 throughout the boring as in the beds at the surface of the reef 

 now forming. The most important rock-forming genera in the 

 order of tlieir relative abundance are Amphistegina, Polytrema, 

 OrhitoUtes, ITeterostegina, Carpeuteria, Gypsina, and C'alcarina. All 

 the forms belong to genera still existing, and no examples of 

 characteristic Tertiary species were recognized. For the determi- 

 nation of critical forms the author acknowledges the invaluable 

 assistance of Mr. F. Chapman. 



Corals, including Alcyonaria and Hydrocorallinte as well as the 

 Madreporaria in this term, are present throughout the main boring, 

 but, especially in the lower 3oU feet, they are more numerous and 

 varied than in the upper part. They have suffered greater changes 

 in fossilization than any other group of organisms, and below a depth 

 of 180 feet in the boring their walls and other structures have been 

 for the most part dissolved and removed, and only casts in sedi- 

 mentary or crystalline materials remain. In many instances they 

 appear to be in the position of growth. Twenty-eight genera have 

 been recorded from the borings ; 22 of these are living at the 

 present time on the reefs or in the lagoon at Funafuti. The 

 commoner genera such as Millepora, Zohophytum, StylopTiora, 

 Pocillopora, Astrcea, Orbicelln, Fangia, Madrepora, Astrceopora, 

 Montipura, and Porites range from the top to the bottom of the 

 main boring, but not continuously, for a particular form which 

 has flourished through a series of consecutive cores will often dis- 

 appear for a variable interval and then come in again. All the 

 forms met with are reef corals ; no examples of deep-water forms 

 have been recognized in any of the cores. 



Of the calcareous Algae the most important genus, Lithothamnion, 

 is represented by branching nodular, and, more especially, by 

 encrusting forms which grow over corals and other oi'ganisms so 

 as to bind them fast together and form layers of very compact 

 dense rock. Another genus, Halimeda, is widely distributed through- 

 out the cores ; in some parts of the main boring and in the boring 

 beneath the floor of the lagoon the rock is mainly composed of 

 their detaclied segments. 



Though the main boring reached to a depth of 1,114 feet it did 

 not penetrate through the reef-rock, and the cores from the bottom 

 were as distinctly reef-like as those from any other part of the 

 boring. 



The last three sections, dealing with the chemical and mineralogical 

 composition of the cores, are of great intei'est. 



First, Professor Judd describes the chemical aspect of the cores 

 as shown in numerous analyses made by his assistants, Dr. C. G. 

 Cullis and Dr. E. W. Skeats, and by Mr. Hart Smith, and this may 

 be generally stated as follows. As far as 637 feet from the surface 

 the core consists of calcium carbonate with a small proportion of 

 magnesium carbonate. Below 637 feet the proportion of magnesium 

 carbonate rises fairly suddenly to nearly 40 per cent, of the whole. 

 Calcium phosphate is present throughout in minute quantities. 



