SECT. 3] 



PELAGIC SEDIMENTS 



683 



now elevated above sea-level and commercially exploited. Complete pseudo- 

 morphous replacement of calcite and aragonite fossils is attained in some cases 

 (Rex, in Hamilton, 1956, p. 35). In contrast to the phosphorite from areas of 

 high productivity, intergrowth with manganese and ferric oxide minerals is 

 common in this type of phosphorite (Fig. 14), but glauconite and organic 



\ 



s ._- 



v.. 



7 



• 'V, •■ ■ 



v.. . 



10 





12 



V. 



■,J«'^„ 



1 



26 



30 



27 



^ -^"^ 



'/^ 



25 



28 





41 



39 







38 



(a) 



19 



20 





43 



44 



■J 



48 



47 



■'•y^ 



/. 



W" 



(b) 



Fig. L5. Fish-bone debris: (a) Diaphane mounting medium, phase contrast. Fish-bone 

 fragments labeled 6 and 48 are teeth, (b) Nuclear emulsion, showing tracks of alpha 

 particles emitted from fish debris, [(b) from Picciotto and Arrhenius, impublished.] 



