418 



DR. C. GILBERT CULLI8. 



Fig. 60. — Conil suljstance eiitirel_y removed ; 

 cavities filled with calcareous detritus alone 

 remaining (phenomenon of reversal). 



Fig. 62. — Coral substance converted into dolo- 

 mite ; cavities empty, except foi' a lining of 

 clear dolomite crystals, separated from the re- 

 crystallised coral hy a well-marked "dirt line." 



Fig. 64. — Coral substance removed by solution ; 

 cavities so formed, as well as the original 

 cavities of the coral, lined with dolomite 

 crystals, the two layers enclosing a fairly well- 

 marked "dirt line'" defining the oiiginal form 

 of the coral. 



Fig. 61. — Coral substance converted into porous 

 mass of acute calcite crystals ; cavities filled 

 with fine calcareous detritus. 



Fig. 63. — Coral-substance dolomite, traveised by 

 " mud "-filled boring-tubes ; cavities partly filled 

 with dolomitised detritus, upper parts lined with 

 clear dolomite civstals. 



Fig. 65.— Coral ca\itie.s filled with fine calcareous 

 detritus ; coral substance then removed by solu- 

 tion, cavities so formed afterwards filled by 

 calcareous detritus ("secondary mud"), and 

 finally the whole dolomitised. 



