Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Matilĭca, ae, f., a city in Umbria, the modern Matelica, Front. de Colon. p. 100 Goes.
Hence, Matilĭcātes, ĭum, m., the inhabitants of Matilica, Plin. 3, 14, 19, § 113.