Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Sīrēna, ae, f., later collat. form of Siren, q. v.; abl. Sirenā, Phil. ad Verg. G. 4, 564; plur., Hier. Ep. 22 (18), 6; 18; Schol. Juv. 9, 150: mortifera Sirenarum carmina, Hier. Ep. 54 (47), 13: cantus Sirenarum, Ambros. de Jac. et Vit. Beat. 2, 12, 56: scopuli Sirenarum, Mart. Cap. 6, § 641: Cyclopum et Sirenarum ora, Tert. Apol. 7 (Oehl. Sirenum).