FORMATIONS AND PHYSICAL HISTORY 405 



\-"\i r .. v=; 7. M up of North America, showing the outcrops of the Onondaga forma- 

 tinn. and the general relations of land and water during the Onondaga epoch. The 

 Devonian at the northwest is not all Onondagan. Note the interrogation marks in 

 the lower Mississippi valley. 



I 



