IV DEPTHS AND DEPOSITS OF THE OCEAN 151 



and iron. It is remarkable how very few fish bones other than 

 teeth and otoHths occur in marine deposits. 



The inorganic materials entering into the composition of Materials of 

 deep-sea deposits may be conveniently considered under three o^J'^frT^''^ 



Fig. 119. 

 Orbuli?ia utiiversa, d'Orbigny. From the surface (%"). 



heads: (i) terrestrial, (2) extra-terrestrial, and (3) secondary or 

 chemical products. 



The terrestrial materials are either of volcanic or continental Terrestrial 

 origin, the former being derived from submarine and subaerial 

 eruptions, and, by reason of their areolar structure, widely 



