Demonian

a. Relating to, or having the nature of, a demon. “Demonian spirits.” Milton. [ 1913 Webster ]

a. (Geol.) Of or pertaining to Devon or Devonshire in England; as, the Devonian rocks, period, or system. [ 1913 Webster ]

Devonian age (Geol.), the age next older than the Carboniferous and later than the Silurian; -- called also the Age of fishes. The various strata of this age compose the Devonian formation or system, and include the old red sandstone of Great Britain. They contain, besides plants and numerous invertebrates, the bony portions of many large and remarkable fishes of extinct groups. See the Diagram under Geology. [ 1913 Webster ]