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TEXTBOOK OF ZOOLOGY 



which were successively penetrated by the drill. Only microscopic 

 specimens persisted, as the drill crushed the others to unrecogniz- 

 able bits. Then came the remarkable rise of the young science of 

 micropaleontology, a field in which women have distinguished them- 

 selves and proved themselves equal to or better than men. 



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Fig. 440. — Diagram to show the vertical distribution of fossils. AjD.OjA.H.O 

 are characters, each indicating a species which has a thousand feet or more definite 

 vertical range. The middle of the figure illustrates the first method described In 

 the text, and the right portion represents the second method. 



Some changes have been made in the classic methods of the 

 science of paleontology, although in the main the newer methods 

 are identifiable as merely refinements of the older. 



Men have long known that some species lived yn the earth much 

 longer than others. In the case of the ordinary marine species, the 



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