In extant Hellenistic-Roman mosaics, Phorcys was depicted as a fish-tailed merman with crab-claw legs and red, spiky skin.

According to Servius, commentator on the Aeneid, who reports a very ancient version already reflected in Varro, distinct from the Greek vulgate:[2] Phorcos was once king of Sardinia and Corsica; annihilated in a naval battle in the Tyrrhenian Sea, and then shot down by King Atlas with a large part of his army, his companions imagined him transformed into a marine deity, perhaps a monster, half man and half sea ram.

[5] Hesiod's Theogony lists the children of Phorcys and Ceto as the Graeae (naming only two: Pemphredo, and Enyo), the Gorgons (Stheno, Euryale and Medusa),[6] probably Echidna (though the text is unclear on this point)[7] and Ceto's "youngest, the awful snake who guards the apples all of gold in the secret places of the dark earth at its great bounds",[8] also called the Drakon Hesperios ("Hesperian Dragon", or dragon of the Hesperides) or Ladon.

These children tend to be consistent across sources, though Ladon is often cited as a child of Echidna by Typhon and therefore Phorcys and Ceto's grandson.

[11] The scholiast on Apollonius of Rhodes cites Phorcys and Ceto as the parents of the Hesperides, but this assertion is not repeated in other ancient sources.