Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. Alcmaeo, Alcmaeon, ŏnis, and Alcmaeus, i, m. (Alcmaeo, Cic. Ac. 2, 28: Alcmaeus, Plaut. Capt. 3, 4, 30), = Ἀλκμαίων, a son of Amphiaraus and Eriphyle; in obedience to the command of his father he killed his mother, and on this account was pursued by the Furies, Hyg. Fab. 71; 73 and 245; Cic. Tusc. 3, 5, 11.
Hence, * Alcmaeŏnĭus, a, um, adj., pertaining to Alcmœon: furiae, Prop. 4, 4, 41.