Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Prăsĭānē, ēs, f., an island in the Indus, Plin. 6, 20, 23, § 71.
Hence, Prăsĭānus, a, um, adj., of or belonging to Prasiane: gens, Plin. 6, 22, 24, § 82.