COLO´NIS an island mentioned by Pliny (Plin. Nat. 4.12. s. 19) as off the coast of Argolis. From the order in which he enumerates the names, and from Colonis occurring in his text in the place of Hydreia ( Tiparenus, Aperopia, Colonis, Aristera, Calauria,), Leake conjectures that Colonis and Hydreia were one and the same island ( Peloponnesiaca, p. 286); but Kiepert gives the name of Colonis to the small island S. of Spétzia.