220 THE SEA FLOOR 



these pelagic plants swarm in the surface waters, 

 as in the extreme northern part of the Pacific and 

 far south in the neighbourhood of the Antarctic 

 circle. The skeletons of Radiolaria and the shells of 

 one or two species of pelagic Foraminifera are usually 

 present, as well as continental mineral particles and 

 ice-borne rock fragments, since this deposit occurs 

 generally within the regions affected by floating ice 

 (Fig. 161). 



In some of the Red Clays and Radiolarian Oozes of 

 the Central Pacific the frustules of the large Diatom 

 Coscinodiscus rex are so abundant that the deposit 

 has sometimes been described as a Diatom Ooze. 



Diatom Ooze is estimated to cover an area of about 

 10,880,000 square miles (or 28,300,000 square kilo- 

 metres) — principally in the Southern Ocean, with a 

 small area in the North Pacific Ocean. 



4. Globigerina Ooze. — This deposit is named from 

 the predominance of the dead shells of Foraminifera, 

 which lived in the surface waters of the ocean, the 

 genus Globigerina (Figs. y8, 162) being the most char- 

 acteristic, though the representatives of other genera 

 are usually present in the tropics (Fig. 163). Associ- 

 ated with the shells of pelagic Foraminifera are the 

 shells of pelagic Molluscs (Pteropods and Heteropods), 

 pelagic calcareous Algae (Coccospheres and Rhabdo- 

 spheres, or their broken fragments — Coccoliths and 

 Rhabdoliths), as well as the remains of calcareous 

 organisms, which habitually live on the bottom of the 

 sea, such as Molluscs, Echinoderms, Annelids, Corals, 

 Polyzoa, and bottom-living Foraminifera. The remains 

 of siliceous organisms (Radiolaria, Diatoms, and Sponge 

 spicules) may generally be detected, and a few small 

 mineral particles, such as felspar, augite, hornblende, 

 magnetite, and volcanic glass, with a small quantity of 



