Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. Hyas, antis (acc. Hyān, Ov. F. 5, 179), m., = Ὕας, a son of Atlas, and father or brother of the Hyades, Hyg. Fab. 192; Ov. F. 5, 170.
Hence, Sidus Hyantis, the Hyades, id. ib. 5, 734.