MINERALOGICAL CHANGES OBSERVED IN CORES OF FUNAFUTI BORINGS. 397 



Fig. 27.— First Boring (SoLLAS). Depth 30-80 feet. 

 X 30. 



" Coral-reef sand " cemented by fibrous encrusting 

 calcite. The minute prismatic elements of the 

 deposit are not disposed in crystalline con- 

 tinuity with the calcite organisms. Compare 

 the investments of the urchin-spines in this 

 figure and in iig. 30. 



Fig. 29.— Main Boring. Core 111. Depth 103 feet. 

 X 100. 



Coral showing cavities containing secondary ara- 

 gonite and calcite. Only one cavity contains 

 calcite, which is of a different type to the fibrous 

 encrusting calcite of figs. 26, 27, and 28, being 

 much more perfectly crystallised. The other 

 cavities contain aragonite deposited in con- 

 tinuity with the fibres of the coral. 



Fig. 28.— Main Boring. Core 36. Depth 30-40 feet. 

 X 100. 



Material intermediate in character between the 

 coarser fragmental accumidations, which contain 

 a large proportion of complete organisms, and 

 the finest detritus. The fragments are cemented 

 by fibrous encrusting calcite. 



Fig. 30.— Main Boring. Core 183. Depth 210- 

 220 feet, x 100. 



The deposition of secondary calcite in crystalline 

 continuity with that of the calcite organisms. 

 Compare the urchin-spine and its investment 

 with those in figs. 27 and 49. 



