280 THE FOEAMINIFEEA 



water of tropical areas may be seen by the observa- 

 tions made by the ' Challenger ' in the South 

 Atlantic Ocean near the equator. Whilst the tempe- 

 rature of the surface water varies between 76° and 80°, 

 at a depth of 300 fathoms it is only 40° ; and in the 

 deeper parts of the same area it is as low as 32-4°. 



Pelagic Deposits. 



Glohifjerina Ooze is the name which was given to 

 the fine, sticky, calcareous mud brought up by the 

 sounding apparatus when testing the ocean contours 

 in order to lay the cables for the electric telegraph. 

 It owes its distinctive name to the comparatively 

 large proportion of shells of Glohiger'oia hulloides 

 and other pelagic Foraminifera of which the deposit 

 largely consists. The dried ooze varies from white, 

 yellow, or rose colour to brown or grey, and it is, 

 obviously, of a darker tint when wet. Those deposits 

 which contain more than 30 per cent, of material 

 directly due to the shells of GJohigei'ina w^ere classed 

 by the ' Challenger' naturalists as Glohigeriua oozes. 

 Besides the pelagic Foraminifera this ooze generally 

 contains a variable quantity of the minute algal bodies 

 known as coccospheres and coccoliths, and rhabdo- 

 spheres and rhabdoliths, together with a small pro- 

 portion of amorphous, calcareous, or earthy matter. 



The Glohigeriua oozes, according to the ' Chal- 

 lenger ' statistics, range in depth from 400 to '2,925 

 fathoms ; but they occur chiefly and typically within 

 the hmits of 1,500 to 2,500 fathoms. 



