FOSSIL CORALS. 



141 



Some of the great Swiss mountains may be just parts of 

 an ancient coral-reef, for though the Jura is some thousands 

 of feet thick, it is but three-quarters of the length of the 

 barrier-reef now existing off the coast of Australia; and 





FIG. 29. NUMMULITIC ROCK, SHOWING SEVERAL SPECIES OF 



FORAMINIFERA. 



although at the present day coral does not grow anywhere 

 north of the Bermudas, it evidently did so in the warmer 

 seas of ancient times, for many of our Devonshire and 

 Bristol marbles are almost entirely composed of fossil 

 corals. 



