Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Ĕpĭmētheus, ei, m., = Ἐπιμηθεύς, in the Greek mythology, a son of Iapetus and Clymene, the husband of Pandora, Hyg. Fab. praef. 142.
Whence his daughter Pyrrha is called Ĕpĭmēthis, ĭdis, f., = Ἐπιμηθίς, Ov. M. 1, 390.