Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† Parthĕnĭae, ārum, m., = Παρθενίαι (maidens’ children), a name given to the colonists of illegitimate birth who emigrated with Phalantus from Sparta and founded Tarentum, the Parthenians, Just. 3, 4, 7 (= spurii, id. 20, 1, 15).