1. The prophetic old man of the sea (halios gerôn), occurs in the earliest legends as a subject of Poseidon, and is described as seeing through the whole depth of the sea, and tending the flocks (the seals) of Poseidon (Hom. Od. iv. 365, 385, 400; Virg. Georg. iv. 392 ; Theocr. ii. 58; Horat. Carm. i. 2. 7; Philostr. Icon. ii. 17). He resided in the island of Pharos, at the distance of one day's journey from the river Aegyptus (Nile), whence he is also called the Egyptian (Hom. Od. iv. 355, 385). Virgil, however, instead of Pharos, mentions the island of Carpathos, between Crete and Rhodes (Georg. iv. 387; comp. Hom. Il. ii. 676), whereas, according to the same poet, Proteus was born in Thessaly (Georg. iv. 390, comp. Ace. xi. 262). His life is described as follows. At midday he rises from the flood, and sleeps in the shadow of the rocks of the coast, and around him lie the monsters of the deep (Hom. Od. iv. 400; Virg. Georg. iv. 395). Anyone wishing to compel him to foretell the future, was obliged to catch hold of him at that time; he, indeed, had the power of assuming every possible shape, in order to escape the necessity of prophesying, but whenever he saw that his endeavours were of no avail, he resumed his usual appearance, and told the truth (Hom. Od. iv. 410, &c. 455, &c.; Ov. Art. Am. i. 761, Fast. i. 369; Philostr. Vit. Apoll. i. 4). When he had finished his prophecy he returned into the sea (Hom. Od. iv. 570). Homer (Od. iv. 365) ascribes to him one daughter, Eidothea, but Strabo (x. p. 472) mentions Cabeiro as a second, and Zenodotus (ap. Eustath. ad Hom. p. 1500) mentions Eurynome instead of Eidothea. He is sometimes represented as riding through the sea, in a chariot drawn by Hippocampae. (Virg. Georg. iv. 389.)
Another set of traditions describes Proteus as a son of Poseidon, and as a king of Egypt, who had two sons, Telegonus and Polygonus or Tmolus. (Apollod. ii. 5. § 9; Tzetz. ad Lyc. 124.) Diodorus however observes (i. 62), that only the Greeks called him Proteus, and that the Egyptians called him Cetes. His wife is called Psamathe (Eurip. Hel. 7) or Torone (Tzetz. ad Lyc. 115), and, besides the above mentioned sons, Theoclymenus and Theonoë are likewise called his children. (Eurip. Hel. 9, 13.) He is said to have hospitably received Dionysus during his wanderings (Apollod. iii. 5. § 1), and Hermes brought to him Helena after her abduction ( Eurip. Hel. 46), or, according to others, Proteus himself took her from Paris, gave to the lover a phantom, and restored the true Helen to Menelaus after his return from Troy. (Tzetz. ad Lyc. 112, 820; Herod. ii. 112, 118.) The story further relates that Proteus was originally an Egyptian, but that he went to Thrace and there married Torone. But as his sons by her used great violence towards strangers, he prayed to his father Poseidon to carry him back to Egypt. Poseidon accordingly opened a chasm in the earth in Pallene, and through a passage passing through the earth under the sea he led him back into Egypt. (Tzetz. ad Lyc. 124; Eustath. ad Hom. p. 686.)
2. A second personage of the name of Proteus is mentioned by Apollodorus (ii. 1. § 5) among the sons of Aegyptus.