CHAPTER V. 



The Process of Fossilization. 



Conditions requisite for f ossi\iza.tion. ^ I^ossilization is the 

 sum of the phenomena by which the remains or impressions 

 of animals or plants are preserved in geologic deposits The 

 first condition required, in order that the organic remains may 

 leave some traces, is that the living organisms to which they 

 belonged should not be too long exposed to the atmosphere 

 during the time immediately following their death. The 

 decomposition of all protoplasmic substances is a matter of cur- 

 rent observation which it is unnecessary to discuss. 



There is only one instance known of extinct animals having 

 been procured intact with their soft parts; that is the example of 

 the Mammoth [Elephas primigenius), found in Siberia in a block 

 of ice which had preserved it from all change. 



Matter possessing greater power of resistance than does the 

 protoplasmic, such as bones, shells and the cellular parts of 

 plants, also decomposes in the air after sufficient exposure. 

 Neumayr cites as an example the interesting fact noticed by 

 Marcou : The Buffaloes are little by little disappearing from 

 the prairies of E'orth America, and are retiring before the 

 increasing population of those countries. But there are still 

 found scattered over the soil skeletons of those animals through- 

 out the regions which they have abandoned during the last twenty 

 years, while from those portions of the country which they left 

 before that time, their remains have almost wholly disappeared. 



The condition essential for the finding of organisms in a fossil 

 state is that the remains should have been either speedily buried 

 in the earth or preserved in water. 



The second of these conditions is not in itself sufficient. The 

 cellular parts are exposed in the water to the attacks of bacteria, 

 and may finally decay without leaving any vestiges. The same 

 may be said of the chitinous or horny parts of animals. On 



