Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Silvĭus, ii, m., the name of several kings of Alba Longa, Liv. 1, 3; Verg. A. 6, 769; Ov. M. 14, 610.
Hence the fem. Silvia; v. 1. Rhea.