GEOLOGIC TIME TABLE (Adapted, with alterations, from Schuchert and Barrell, American 



Journal of Science, 1914) 



* The modern era, called by Schuchert and Barrell Psychozoic, is not a true era comparable with the 

 others, but ought in all reason to be considered part of the Cenozoic. 



t The insects are so well developed in the Pennsylvanian, that their actual origin must be much earlier. 



148 



