1911 Encyclopædia Britannica/Glaucus 2.
2. Glaucus, usually surnamed Potnieus, from Potniae near Thebes, son of Sisyphus by Merope and father of Bellerophon. According to the legend he was torn to pieces by his own mares (Virgil, Georgics, iii. 267; Hyginus, Fab. 250, 273). On the isthmus of Corinth, and also at Olympia and Nemea, he was worshipped as Taraxippus (“terrifier of horses”), his ghost being said to appear and frighten the horses at the games (Pausanias vi. 20). He is closely akin to Glaucus Pontius, the frantic horses of the one probably representing the stormy waves, the other the sea in its calmer mood. He also was the subject of a lost drama of Aeschylus.
All the above are exhaustively treated by R. Gaedechens in Ersch and Gruber’s Allgemeine Encyclopädie.