236 MAYOR— THE REEFS OF TUTUILA, SAMOA. 



It seems probable that the reefs now living in the Pacific are 

 structures which have originated in modern times upon submerged 

 slopes and platforms of marine erosion. Being not more than 

 40,000 years old, these reefs have not existed long enough to have 

 been subjected, except in rare instances, to appreciable subsidence 

 or elevation of the land masses upon which they have attained a 

 foothold. 



GuYOT Hall, 



Princeton University. 



