Lewis & Short

2. Phorcus, i (also Phorcys, yos, and Phorcyn, ȳnos, acc. to Prisc. p. 690 P., but acc. to Serv., Verg. A. 5, 240, these forms are not used in Lat.), m., = Φόρκος, Φόρκυς, and Φόρκυν, son of Neptune, father of Medusa and the other Gorgons, and of the Grœœ, who was changed after death into a sea-god, Cic. Univ. 11, 35: Phorci chorus, Verg. A. 5, 240; or, Phorci exercitus, i. e. sea-gods, id. ib. 5, 824: pater Phorcys, Val. Fl. 3, 726; Luc. 9, 645.
Hence,

  1. A. Phorcys, ydos (Phorcis, ĭdis), f., a female descendant of Phorcus: ora Phorcydos, i. e. of Medusa, Prop. 3, 21 (4, 22), 8: geminas habitasse sorores Phorcydas unius partitas luminis usum, i. e. the Grœœ, Ov. M. 4, 773.
  2. B. Phorcȳnis, ĭdos and ĭdis, f., the daughter of Phorcus, i. e. Medu- sa, Ov. M. 5, 230; Luc. 9, 626.