Story of the Mississippi- Missouri. — Claypole. 
363 
of its shores and in its depth but speaking of the region as a 
whole it was occupied by sea from a very early date in the 
palaeozoic history to its end. 
The annexed table will render the sequence of geologic time clear to 
the reader. The increasing spaces downward may be taken to rudely 
represent the greater length of the eras. 
Post-Tertiary. 
Pliocene. 
Miocene. 
Eocene. 
Cretaceous. 
Tertiary. 
Mesozoic. 
Jurassic. 
Triassic. 
Carboniferous. 
Devonian . 
Palaeozoic 
Silurian. 
Ordovician. 
Cambrian. 
Huronian, 
Archaean. 
Laurentian, upper. 
Laurentian, lower. 
The Cambrian age had already passed away and we have 
little or no knowledge of the condition of the continent dur- 
