Lewis & Short

Lārĭus, ii, m., a lake in Gallia Cisalpina, on which Comum lay, now Lago di Como, Verg. G. 2, 159; Plin. Ep. 9, 7, 1; Plin. 3, 19, 23, § 131.
Hence, Lārĭus, a, um, adj., of Larius, Larian: Larium litus, Cat. 35, 4.