Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
† pĕristrōma, ătis, n., = περίστρωμα, a covering, curtain, carpet: Babylonia peristromata, Plaut. Stich. 2, 2, 54; id. Ps. 1, 2, 12: conchyliata peristromata, Cic. Phil. 2, 27, 67.