Ill 



PRE-CAMBRIAN LIFE 



T T AVING traced the chain of life through the 

 long geological ages, from the present day 

 back to the Cambrian Period, we may now take 

 our stand on the fauna of the lowest Cambrian 

 or Olenellus Zone, as a platform whence we may 

 dive into still deeper abysses of past time. Here, 

 however, we seem to have arrived at a limit beyond 

 which few remains of living things have yet been 

 discovered, though there still remain pre-Cambrian 

 deposits of vast thickness and occupying large areas 

 of our continents. These pre-Cambrian formations 

 are as yet among those least known to geologists. 

 The absence of fossils, the disturbances and alter- 

 ations which the rocks themselves have undergone, 

 and which make their relative ages and arrangement 

 difficult to unravel, have acted as deterrents to 

 amateur geologists, and have to some extent baffled 

 the efforts of official explorers. In addition to this, 

 workers in different regions have adopted different 



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