PRINCIPLES OF PALEONTOLOGIC CORRELATION 697 



If there had ever been any great displacement of the faunal 

 scale from the time scale, this would have been cumulative, and 

 eventually the paleontologic column of America would have 

 been out of harmony with that of Europe. But the successive 

 faunas from Lower Cambrian to Pleistocene are in perfect 

 accord in all the regions of Europe, Asia, Africa, America, and 

 Australia; there are constantly recurring small displacements due 

 to temporary isolation, and constantly recurring readjustment due 

 to reopened or newly-formed connections, giving interregional 

 correlative faunal zones through migration. These zones may be, 

 and often are,, actually synchronous. The periods of endemic 

 development may be homotaxial, but the zones of readjustment 

 are correlative in the strictest sense. 



James Perrin Smith. 



Stanford University, California. 



