CHAPTER II 

 MATERIALS 



(A) THE NATURE OF FOSSILS 



(I) DEFINITION OF TERMS "FOSSIL" AND 

 " PETRIFACTION " 



THE name "fossil," which means "a thing dug up," 

 was applied by early Geologists to objects that could 

 be extracted from rocks, but that were not strictly 

 samples of the rocks. It thus comprised separable 

 minerals (particularly those in veins or geodes) as well 

 as the curiously shaped "stones," of organic origin, 

 as to whose characters much controversy existed. 

 These two kinds of fossils were distinguished by the 

 adjectives " native " and " extraneous " respectively, the 

 latter types being clearly distinct from, and largely 

 independent of, the rocks enclosing them. When con- 

 tinued study had plainly demonstrated the biological 

 qualities of "extraneous" fossils, that non-committal 

 adjective was replaced by the word "organized," and 

 the expression " organic remains " became generally 

 employed. At about the same time the term "petri- 

 faction " came into frequent use, indicating that fossils 

 had often become mineralized during entombment in 

 the rocks. Gradually application of the word " fossil " 

 to purely mineral specimens dropped out, and with its 

 restriction to the " organized " kinds, need for qualifying 

 adjectives disappeared. In its modern usage the word 



