ποταμίας ... Ἀρτέμιδος: Artemis, among her numerous functions, is a river-goddess, and in the Peloponnesos her worship is connected especially with the Kladeos and the Alpheios (Ἄρτεμις Ἀλφειῴα). She has charge of rivers not only as a huntress, but as the representative of the Oriental Artemis. Pursued by Alpheios, she fled under the waters of the Ionian sea, and found rest by the fountain of Arethusa in Ortygia, where a temple was raised in her honor. Of course, Arethusa and Artemis are one (compare Telesilla, fr. 1: ἅδ᾽ Ἄρτεμις, ὦ κόραι, ι φεύγοισα τὸν Ἀλφεόν), but when Alpheios and Arethusa were united, Artemis, the virgin, and Arethusa were separated. Similar is the case of Kallisto. Compare with this whole passage N. 1.1: ἄμπνευμα σεμνὸν Ἀλφεοῦ, ι κλεινᾶν Συρακοσσᾶν θάλος Ὀρτυγία, ι δέμνιον Ἀρτέμιδος, ι Δάλου κασιγνήτα. Note also that the brother of Artemis appears in the corresponding sweep of the antistrophe.
ἇς οὐκ ἄτερ: O. 3.26: Λατοῦς ἱπποσόα θυγάτηρ, fr. V. 2, 2: ἵππων ἐλάτειραν. Hieron has a trinity of helpers, Ἄρτεμις ποταμία, Ἑρμῆς ἐναγώνιος, and κλυτόπωλος Ποσειδάων (fr. XI. 33, 2), whose enmity was so fatal to Hippolytos, favorite though he was of Artemis.
