The Refutation of All Heresies: Book V. 21The Cosmogony of Justinus an Allegorical Explanation of Herodotus' Legend of Hercules.

Herodotus, then, asserts that Hercules, when driving the oxen of Geryon from Erytheia, came into Scythia, and that, being wearied with travelling, he retired into some desert spot and slept for a short time. But while he slumbered his horse disappeared, seated on which he had performed his lengthened journey. On being aroused from repose, he, however, instituted a diligent search through the desert, endeavouring to discover his horse. And though he is unsuccessful in his search after the horse, he yet finds in the desert a certain damsel, half of whose form was that of woman, and proceeded to question her if she had seen the horse anywhere. The girl, however, replies that she had seen (the animal), but that she would not show him unless Hercules previously would come along with her for the purpose of sexual intercourse. Now Herodotus informs us that her upper parts as far as the groin were those of a virgin, but that everything below the body after the groin presented some horrible appearance of a snake. In anxiety, however, for the discovery of his horse, Hercules complies with the monster's request; for he knew her (carnally), and made her pregnant. And he foretold, after coition, that she had by him in her womb three children at the same time, who were destined to become illustrious. And he ordered that she, on bringing forth, should impose on the children as soon as born the following names: Agathyrsus, Gelonus, and Scytha. And as the reward of this (favour) receiving his horse from the beast-like damsel, he went on his way, taking with him the cattle also. But after these (details), Herodotus has a protracted account; adieu, however, to it for the present. But what the opinions are of Justinus, who transfers this legend into (his account of) the generation of the universe, we shall explain.