POLYXO was a Naiad-nymph of Libya or Egypt, one of the many wives of the Libyan prince Danaus. Their twelve Danaid daughters married the twelve sons of her Naiad sister Kaliadne (Caliadne).
Perhaps a daughter of the River NEILOS
AUTONOE, THEANO, ELEKTRA, KLEOPATRA, EURYDIKE, GLAUKIPPE, ANTHELEIA, KLEODORE, EUIPPE, ERATO, STYGNE, BRYKE (by Danaus) (Apollodorus 2.19)
POLYXO (Poluxô). A nymph married to Danaus. (Apollod. ii. 1. § 5.)
Source: Dictionary of Greek and Roman Biography and Mythology.
CLASSICAL LITERATURE QUOTES
Pseudo-Apollodorus, Bibliotheca 2. 19 (trans. Aldrich) (Greek mythographer C2nd A.D.) :
"The twelve sons of a Naias Nymphe (Naiad Nymph) named Kaliadne (Caliadne) [and King Aigyptos (Aegyptus)] drew lots for the daughters of Polyxo, also a Naias (Naiad) [and King Danaus of Argos]. The sons were named Eurylokhos (Eurylochus), Phantes, Peristhenes, Hermos (Hermus), Dryas, Potamon, Kisseus (Cisseus), Lixos, Imbros, Bromios, Polyktor (Polyctor), and Khthonios (Chthonius); the girls were Autonoe, Theano, Elektra (Electra), Kleopatra (Cleopatra), Eurydike (Eurydice), Glaukippe (Glaucippe), Antheleia, Kleodore (Cleodora), Euippe, Erato, Stygne, and Bryke (Bryce)."
- Apollodorus, The Library - Greek Mythography C2nd A.D.