Passage 2.18.6
Λακεδαιμονίων δὲ ἐβασίλευσεν Ὀρέστης Λακεδαιμονίων ἐφέντων αὐτῷ· τοὺς γὰρ Τυνδάρεω θυγατριδοῦς τὴν ἀρχὴν ἔχειν οὐκ ἠξίουν πρὸ Νικοστράτου καὶ Μεγαπένθους Μενελάῳ γεγενημένων ἐκ δούλης. Ὀρέστου δὲ ἀποθανόντος ἔσχε Τισαμενὸς τὴν ἀρχήν, Ἑρμιόνης τῆς Μενελάου καὶ Ὀρέστου παῖς. τὸν δὲ Ὀρέστου νόθον Πενθίλον Κιναίθων ἔγραψεν ἐν τοῖς ἔπεσιν Ἠριγόνην τὴν Αἰγίσθου τεκεῖν.
After the Spartans appointed him king, Orestes ruled over the Lacedaemonians; for it was not considered proper by them that the sons of the daughter of Tyndareus should hold power, since Nicostratus and Megapenthes had been born to Menelaus by a slave woman. After the death of Orestes, Tisamenus, the son of Orestes and Hermione, Menelaus' daughter, obtained the kingship. As for Orestes' illegitimate son, Penthilus, Cinaethon wrote in his poetry that Erigone, the daughter of Aegisthus, was his mother.