ABYSSAL BENTHAL AND PELAGIAL 



251 



The terrigenous deposits vary in nature. In the East Indian waters, 

 where such deposits are abundant, they may have a rich fauna. On 

 the contrary, Chun reports the river mud of the Gulf of Guinea as poor 

 in animal life. Single groups may thrive on a special type of bottom. 

 The glass sponges (Hexactinellidae) 8 with their siliceous skeleton do 



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Fig. 63 



Fig. 64 



Fig. 63. — Rhizocrinus lofotensis, a stalked crinoid of the deep sea. After Boas. 

 Fig. 64. — Chlidonophora chuni, a long stalked brachiopod from the deep sea. 



After Blochmann. 



best on siliceous deposits, diatomaceous ooze ranking first, radiolarian 

 ooze next, and blue, deep-sea ooze, third; the last is a quartzitic 

 terrigenous deposit. 



Deep-sea ooze may be compared in appearance and consistency to 

 butter in summer. Animals living on it require some means of support. 

 An enlargement of surface, and, in animals with legs, a distribution of 



