at last he came to the region which is called Hylaia; and there he found in a cave a kind of twofold creature formed by the union of a maiden and a serpent, whose upper parts from the buttocks upwards were those of a woman, but her lower parts were those of a snake. Having seen her and marvelled at her, he asked her then whether she had seen any mares straying anywhere; and she said that she had them herself and would not give them up until he lay with her; and Heracles lay with her on condition of receiving them