GEOGEAPHICAL DISTEIBUTION, ETC. 287 



Sydney at 410 fathoiDS. The deposit resembles a 

 grey ooze : — 



' The organisms contained in the material from 

 this station are infiltrated in a very remarkable 

 manner with a siliceous mineral (Glauconite), and 

 by decalcifying with weak acid perfect casts of the 

 chambers of most of the Foraminifera of a common 

 Glohigeruia ooze may be obtained. The list of 

 species is a tolerably long one, and contains an 

 admixture of some shallow-water forms, but other- 

 wise presents nothing very distinctive.' 



In consideration of the fact that Greensands 

 occur as important foraminiferal deposits in various 

 geological systems it is interesting to note that at 

 the present day these deposits are never found deeper 

 than 900 fathoms, whilst their average depth is 

 449 fathoms. For the formation of these deposits it 

 seems essential that they should be within the in- 

 fluence of marine currents by which the sands are set 

 in motion. Extensive deposits of Greensands are met 

 with off the coast of California, the east coast of 

 N. America, the Cape of Good Hope, to the east 

 of Africa, and off' the coasts of Portugal, South 

 America, Japan, and Australia. 



The deposits forming round coral islands in the 

 Pacific and Indian Oceans are known as Coral MikIh 

 and Coi-dl Sdiid. They are largely made up of the 

 organisms which live in great numbers in such locali- 

 ties, as, for example, the Calcareous Algie, various 

 Foraminifera, Alcyonarians, Corals, Molluscs, Poly- 

 zoa, Annelids, and Echinoderms. 



