Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† chĕlȳ̆drus, i, m., = χέλυδρος, a fetid serpent, living, for the most part, in water, Cels. 5, 27, 8; Verg. G. 3, 415; Ov. M. 7, 272; Luc. 9, 710; Sil. 3, 316; 8, 496; Prud. c. Symm. 1, 130.