Lewis & Short

Phŏrōneus (trisyll.), ĕi and ĕos, m., = Φορωνεύς, son of Inachus, king of Argos, and brother of Io, Hyg. Fab. 124; 143; 225; 274; Plin. 7, 56, 57, § 193; Stat. Th. 4, 889.
Hence,

  1. A. Phŏrōnēus, a, um, adj., Phoronean, poet. for Argive: Phoroneis sub antris, Stat. S. 3, 2, 101.
  2. B. Phŏrō-nis, ĭdis, f. adj., Phoronean, poet. for Argive: Phoronides latuere venae, i. e. the river Inachus, Sen. Thyest. 115.
    Subst.: Phorōnis, ĭdis, f., Io, Ov. M. 1, 668; 2, 524.