Simple scale showing the division and chronology of geologic time as it is understood in North America. The Devonian Period occurred from roughly 410-360 million years ago, though opinions differ on the exact years.
Decade of North American Geology
United States Geological Survey, National Park Service, Department of the Interior
North America, Prehistory
“Geologic Timescale,” Winifred Goldring, State Paleontologist, accessed May 21, 2018, http://goldring.omeka.net/items/show/3.