This mountain-chain called Bermius, extending from Olympus considerably to the north of Edessa, formed the original eastern boundary of the Macedonian tribes; who seem at first not to have reached the valley of the Axius in any part of its course, and who certainly did not reach at first to the Thermaic gulf. Between the last-mentioned gulf and the eastern counterforts of Olympus and Bermius there exists a narrow strip of plain land or low hill, which reaches from the mouth of the Peneius to the head of the Thermaic gulf. It there widens into the spacious and fertile plain of Salonichi, comprising the mouths of the Haliakmôn, the Axius, and the Echeidôrus: the river Ludias, which flows from Edessa into the marshes surrounding Pella, and which in antiquity joined the Haliakmôn near its mouth, has now altered its course so as to join the Axius. This narrow strip, between the mouths of the Peneius and the Haliakmôn, was the original abode of the Pierian Thracians, who dwelt close to the foot of Olympus, and among whom the worship of the Muses seems to have been a primitive characteristic; Grecian poetry teems with local allusions and epithets which appear traceable to this early fact, though we are unable to follow it in detail. North of the Pierians, from the mouth of the Haliakmôn to that of the Axius, dwelt the Bottiæans.[22] Beyond the river Axius, at the lower part of its course, began the tribes of the great Thracian race,—Mygdonians, Krestônians, Edônians, Bisaltæ, Sithonians: the Mygdonians seem to have been originally the most powerful, since the country still continued to be called by their name, Mygdonia, even after the Macedonian conquest. These, and various other Thracian tribes, originally occupied most part of the country between the mouth of the Axius and that of the Strymon; together with that memorable three-pronged peninsula which derived from the Grecian colonies its name of Chalkidikê. It will thus appear, if we consider the Bottiæans as well as the Pierians to be Thracians, that the Thracian race extended originally southward as far as the mouth of the Peneius: the Bottiæans professed, indeed, a Kretan origin, but this pretension is not noticed by either Herodotus or Thucydidês. In the time of Skylax,[23] seemingly during the early reign of Philip the son of Amyntas, Macedonia and Thrace were separated by the Strymon.