THE 



JOURNAL OF GEOLOGY 



NOVEMBER-DECEMBER, igoo 



PRINCIPLES OF PALEONTOLOGIC CORRELATION. 1 



CONTENTS 

 General discussion. 

 Paleontologic zones. 



Dispersion of marine animals in past and present. 

 Colonies. 



Synchronism vs. Homotaxis. 

 The reality of correlation. 



General discnssio?i. — Geologic correlation has been carried on 

 ever since the pupils of Werner endeavored to recognize his 

 stratigraphic divisions in remote parts of the earth ; and since 

 William Smith discovered that fossils are characteristic of cer- 

 tain formations, paleontologic correlation has been attempted. 

 Still it must not be forgotten that the greater part of the cor- 

 relation that has been done up to this time is based on litho- 

 logic and stratigraphic rather than on fauna! data. Fossils 

 have been regarded as incidental, useful in recognizing strata, 

 but not as a basis for subdivisions on account of changes in 

 fauna or flora. 



Where a rock-bed of distinctive character is persistent over 

 a wide extent of country, a lithologic correlation would reach as 

 good, and often even better, results than could be obtained from 



'Read before Section E. Amer. Assoc. Adv. Sci., June 28, 1900. 

 Vol. VIII, No. 8. 673 



