600 



Miss M. B. Chapman- 



structure has since disappeared, as the Brachiopods and some Corals 

 still remain without the loss of their structure. 



It is therefore a chemically pure limestone which nowhere exhibits 

 the structure of a coral reef. 



li. Passage beds hettveen K and Z zones. 



Total 



aoo-09 



The insoluble residue consists chiefly of detrital quartz and black 

 carbonaceous material. Analyses of different parts of these beds gave 

 very constant results, the amount of insoluble residue only varying 

 between 4-78 per cent and 4*96 per cent. 



Total . . 99-93 100-08 



A. and B are analyses of those specimens which have the greatest 

 and least amount of insoluble residue. This residue consists of 

 detrital quartz, quartz with secondary deposition of silica, small 

 zircons, and some pyrites ; most of the material was much rounded, 

 as if by current action or under littoral conditions. 



Z2. Zaphrentis Tconincki subzone. 



CaO 55-63 



MgO 1-73 



CO2 42-22 



Fe2 O3 + AI2 O3 . . . . -29 



Insoluble residue . . . . -43 



Total . . 100-30 

 The percentage of insoluble residue varies from '37 to "46 — most 

 of this is silica ; secondary deposition has often formed perfect doubly 

 terminated crystals. Minute zircons, fragments of tourmaline, some 

 carbonaceous material, and small quartz flakes also occur. 

 Marked coral bands occur througliout this subzone. 



7. Passage beds between zones Z and C. 

 CaO . . . . . . 41-99 



Mg O 



CO. 



Feo O3 + AI2 0, 



Insoluble residue 



10-68 



41-43 



•93 



4-95 



Total . 



99-98 



