In Greek mythology, Melia is the Oceanid who, by her brother the river-god Inachus, becomes mother of Phoroneus and Aegialeus — the first Argive line in Apollodorus. Her name is shared with several other Meliai (Theban cult partner of Apollo, Bithynian mother of Amycus, and the ash-tree nymphs as a class); the atlas node is the Argive Oceanid.
Adapted from Wikipedia, "Melia (mythology)" · CC BY-SA 4.0
I.Mother of the Argive line
Apollodorus states that of Inachus and Melia, daughter of Oceanus, were born Phoroneus and Aegialeus. Through Phoroneus — first man and king of the land later called the Peloponnese — she stands at the root of the Argive stem that leads to Apis, Niobe, and the Danaid generations.
Hyginus replaces her: Inachus begets Phoroneus by his sister Argia, another Oceanid, and Melia drops from the Argive tree. Pausanias' local Argive notices name no mother for Phoroneus at all — so the first king's maternity remains a live contradiction among the sources.
II.Other Meliai
Wikipedia's Melia index also covers the Theban Melia (mother of Tenerus and Ismenus by Apollo), a Bithynian Melia mother of Amycus by Poseidon, Callimachus' Melia mother of Keos, and Pherecydes' Tyrian and Niobid namesakes. The plural Meliae are the ash-tree nymphs of Hesiodic cosmogony.
The atlas id melia, with kinds oceanid, is reserved for Inachus' Argive partner — not the Theban or Bebrycian figures.