THE AKHELOIDES (or Acheloides) were the Naiad Nymphs of the River Akheloios in Aitolia (central Greece).

Three of their number, the Seirenes, were close companions of Persephone. When their mistress was abducted by Haides they were given the bodies of birds to assist them in their search for the goddess.

"[The River-God welcomed Theseus into his underwater palace] Of porous pumice and rough tufa-rock the residence was built. The floor was damp and soft with moss, the ceiling diapered with shells of conch and murex laid in turn ... Theseus with his company reclined on couches ... Soon barefoot Nymphae [the Akheloides] arranged the tables and spread the banquet-board, and when the feast was cleared they set a jewelled bowl of wine." - Ovid, Metamorphoses 8.568

"[Akhelous tells Theseus the tale of his encounter with Herakles:] 'He [Herakles] grasped my strong stiff horn in his fierce hand, broke it, and wrenched it off - my brow was maimed! My Naides filled it full of fragrant flowers and fruits, and hallowed it. From my honour now Bona Copia (Good Plenty) finds her wealth and riches flow.’ His [Akhelous'] tale was done. One of the serving Nympha, dressed in Diana’s [Artemis’] simple style, her hair flowing on either side, came bearing in the horn with all its wealth, all autumn there, fruits in perfection for our second course." - Ovid, Metamorphoses 9.86

"The River Achelous used to change himself into all sorts of shapes. When he fought with Hercules to win Dejanira in marriage, he changed himself into a bull. Hercules tore off his horn, presenting it to the Hesperides or the Nymphae [the Akheloides], and the goddesses filled it with fruits and called it Cornucopia." - Hyginus, Fabulae 31

Sources:

• Hyginus, Fabulae - Latin Mythography C2nd AD
• Ovid, Metamorphoses - Latin Epic C1st BC - C1st AD

Other references not currently quoted here: Columella On Country Matters 10.263