TABLE OF STRATIFIED ROCKS 



SHOWING APPROXIMATE THICKNESS. 



TOTAL DEPTHS. quatcbn 



I3.3S0 

 W.8S0 



Fig. 41. — A tabular 

 view of the strata 

 of the earth's 

 crust, showing the 

 relative thickness 

 of each " system " 

 or grovip of strata, 

 and the position 

 in whicli impor- 

 tant animal re- 



SYSTEMS 



— :- _z- -SILURIAN — — _:- _r 



-~—~—Z-. zbo'o ft'—~—~-Zs 



'I'j.r'i/iJil'/W,-/-/', 



.//./•//////•/•/•////■/ 



/', , OR DO V I C I A N /•/•/ 



///,/y-;,7„/A''///'%. 



TYPICAL FORMS'. 



HOBStb i MAMMALS CESERAL 

 LAST ICHTHYOEAUBS 

 CREAT DINOSAURS 



VST TBILOBITEJ 



SCOBPiONS 



o a 

 S O 



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FIRST TRILOBITES 



mains have been 

 discovered. The 

 rocks are never 

 found lying hori- 

 zontally like this, 

 which is a diagram. 

 In nature they are 

 tilted and crum- 

 pled, but we can 

 make out their 

 thickness and the 

 order in which they 

 lie one over the 

 other. 



