Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† thēca, ae, f., = θήκη, that in which any thing is enclosed, an envelope, hull, cover, case, sheath, etc. (syn. vagina): grani, Varr. R. R. 1, 48, 1: efferri sine thecis vasa, Cic. Verr. 2, 4, 23, § 52; id. Att. 4, 7, 2; Quint. 6, 3, 61: calamaria, Suet. Claud. 35; Mart. 14, 19, 1; Amm. 28, 4, 13.