Presumably daughters of the local RIVER-GOD
MEGAROS (a Sithnis Nymphe by Zeus) (Pausanias 1.40.1)
CLASSICAL LITERATURE QUOTES
Pausanias, Description of Greece 1. 40. 1 (trans. Jones) (Greek travelogue C2nd A.D.) :
"There is in the city [of Megara] a fountain, which was built for the citizens by Theagenes . . . This Theagenes upon becoming tyrant built the fountain, which is noteworthy for its size, beauty and the number of its pillars. Water flows into it called the water of the Nymphai (Nymphs) Sithnides. The Megarians say that the Nymphai Sithnides are native, and that one of them mated with Zeus; that Megaros (Megarus), a son of Zeus and of this Nymphe, escaped the flood in the time of Deukalion (Deucalion), and made his escape to the heights of Gerania. The mountain had not yet received this name, but was then named Gerania (Crane Hill) because cranes were flying and Megaros swam towards the cry of the birds."
- Pausanias, Description of Greece - Greek Travelogue C2nd A.D.