344 ALEXANDER AGASSIZ 



with anything after the great alteration that has taken 

 place in depth by calcite. The mere statement that the 

 corals are identical goes for nothing. If, as I think, the 

 underlying limestone beds of the modern reef are of Ter- 

 tiary age, as in Fiji and Christmas Island, the difficulty 

 of separating the modern corals and the Tertiary ones 

 is very great and difficult even where these rocks are 

 accessible. I don't think the line of demarcation can be 

 determined by a core where it is drawn between forma- 

 tions with fossils so closely allied to the recent types. 

 The boring should be done in a region where volcanic 

 beds are underlying the coral reefs." 



