SCYLLA THE TRADITION:

In Homer Scylla is a twelve-footed, six-headed monster who feeds on dolphins and sailors, and poses a menace to Odysseus and his men.Hom. Od. 12.73-126.2  According to another tradition, she poaches Geryon’s cattle as Heracles is conveying them back to Greece, which leads Heracles to kill her; her body is then burnt by her father, which results in her resurrection.Dionysius of Samos FGrHist 15 F 12, Lyc. Alex. 44-9, Tzetzes on Lyc. Alex.46 (11 34.25-35.4, 35.18-27 Scheer).  She does not appear in art before the second half of the fifth century.See further Fontenrose (1959) 97-100, Jentel (1997), Ogden (2013) 129-35,Hopman (2013).

Scylla’s mother is called Crataeis by Homer,Hom. Od. 12.124—5; thus Ov. Met. 13.749, Apollod. Bibl. 7.20, = Pl. Resp.588c (p. 270 Greene), etc.5 [Hes.] fr. 262 M-W; thus Acusilaus fr. 42 EGM, Dionysius, and the scholia to Lucian. Hecate in the Hesiodic Catalogue. Apollonius conflates the two traditions,Ap. Rh. 4.828-9. while Hyginus prefers Echidna.Hyg. Fab. 151.1; praef. 39. As for her father (not mentioned by Homer), the best-supported candidate is Phorcys,Thus Acusilaus, Dionysius, Apollonius, Apollodorus, and the Platonic and Lucianic scholia, as cited above. This figure is probably the same as the Φόρκος and Πόρκος who appear in other early texts; see West on Hes. Th.237. son of Pontos and brother of Nereus, Old Man of the Sea.Hes. Th. 233-9. Hesiod makes Phorcys and his sister; the aptly-named Ceto (Κητώ, ‘Sea-monster’), the parents of a brood of monsters;Ibid. 270-336: the Graiai, Gorgons, Echidna, and a snake. He does not mention Scylla. elsewhere he fathers Thoosa, mother of Polyphemus, and the Sirens.Hom. Od. 1.712; Soph. fr. 861 TrGF.510 Eustathius calls Scylla’s father Triton, a figure himself associated with Phorcys.Eust. Od. 1714.33–4 (ii 13.23–4 Stallbaum). Hes. Th. 930–3 makes Triton the son of Poseidon and Amphitrite; cf. Virg. Aen. 5.824 Tritonesque citi Phorcique exercitus omnis, Plin. NH 36.26 Tritones chorusque Phorci. Alternatives include Phorbas, Tyrrhenus, and Typhon.Thus respectively [Hesiod], the Platonic scholia, and Hyginus (praef. 39, 125.14, 151.1). At Hes. Th. 304–15 Typhon fathers monstrous children on Phorcys’ daughter Echidna. Apollod. Ep. 7.20 mentions Trienus as a variant for Phorcus; this may be an error for Tyrrhenus or Typhon.