THE PHYSICAL CONDITIONS OF THE ABYSS 39 



rninifera. This is supported by the fact that it 

 extends ten degrees further north than south in the 

 Atlantic, the warm water of the Gulf Stream bear- 

 ing a richer fauna than the waters of a corresponding 

 degree of latitude in the Southern Sea. 



The Pteropod ooze has only twenty-five per cent, 

 of carbonate of lime. It contains numerous shells 

 of various Pteropods, Heteropods, and Foramini- 

 fera, but nearly fifty per cent, of its substance is com- 

 posed of the siliceous skeletons of Radiolaria and the 

 frustules of diatoms. 



According to Murray it is found in tropical 

 and subtropical seas at depths of less than 1,500 

 fathoms. 



The Radiolarian ooze is found only in the deepest 

 waters of the Central and Western Pacific Ocean. In 

 some of the typical examples, not a trace of carbonate 

 of lime was to be found, but in somewhat shallower 

 waters a few small fragments occurred. 



A Diatom ooze, mainly composed of the skeletons 

 of diatoms, has also been found in deep water near the 

 Antarctic Circle, but it has not apparently a very wide 

 range. 



Of all the deep-sea deposits, however, the so- 

 called ' Red mud ' has by far the widest distribution. 



