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SHELLS OF FORAMIXIFERA. 



shells — gradually sink to the bottom, where they form a 

 fine grayish mud, which has been found to be spread over 

 wide areas in the bed of the Atlantic. To know what this 

 fine mud will, in all probability, one day become, w^e have 

 only to go to the south of England, and there, beneath the 



F0RA3IINIFERA. 



surface of the soil, the solid rock over a wide area is seen 

 to consist of pure chalk. Eeduce a small piece of this to 

 powder, mix it with water, and then look at it with a 

 strongly magnifying glass ; it will then be seen to consist 

 entirely of the minute shells of foraminifera, — in other 

 words, to be identical with the whitish mud that is now 



