Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Callisto, ūs (ōnis, Serv. ad. Verg. G. 1, 67), f., = Καλλιστώ, daughter of the Arcadian king Lycaon (hence, Lycaonis, Ov. F. 2, 173: virgo Tegeaea, id. ib. 2, 167: Maenalia, id. ib. 2, 192: virgo Nonacrina, id. M. 2, 409), and mother of Arcas by Jupiter; changed by Juno, on account of jealousy, into a she-bear, and then raised to the heavens by Jupiter in the form of the constellation Helice or Ursa Major, Hyg. Fab. 176; 177; Prop. 2 (3), 28, 23; Col. 11, 2, 15; Ov. F. 2, 156 sq.; cf. id. M. 2, 401 sq.
Acc. Callisto, Hyg. Astr. 2, 1.
Dat. Callisto Lycaonidi, Cat. 66, 66.
Abl. Callisto, Hyg. Fab. 155.