CHAPTER XV. 



THE FORMATION OF LAND BY ANIMAL AGENCIES — CORAL 



LAND. 



It has already been pointed out that when an aquatic 

 animal dies, its hard parts, such as a shell, or bones, if it 

 happen to possess any, will stand a fair chance of consti- 

 tuting a permanent contribution to the solid materials of 

 the earth, by becoming embedded in mud, and in this way 

 preserved from destruction. 



Such names as " Shell-haven," near Tilbury, on the Essex 

 coast, and " Shell-ness," in the Isle of Sheppey, sufficiently 

 indicate the abundance of shells, which accumulate in certain 

 regions of the estuary of the Thames ; and, on many other 

 parts of the English coast, enormous multitudes of shells are 

 scattered upon the sea-beach and embedded in its sands 

 and mud. 



Vast quantities of dead shells accumulate on oyster-beds, 

 and the dredge brings up similar objects, wherever it is 

 allowed to scrape along the bottom of the sea, around our 

 coasts. Moreover, in some parts of the Channel, small 

 reefs are built up of nothing but the sandy habitations which 

 are fabricated by certain marine worms. 



This operation of the formation of new land by ani- 

 mal agents is manifested in the most conspicuous 



