Nep·tu·ni·an prop. a.
 1. Of or pertaining to the ocean or sea.
 2. Geol. Formed by water or aqueous solution; as, Neptunian rocks.
 Neptunian races Ethnol., the Malay and Polynesian races.
 Neptunian theory Geol., the theory of Werner, which referred the formation of all rocks and strata to the agency of water; -- opposed to the Plutonic theory.
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