Illustrated Companion to the Latin Dictionary/Operculum

This article incorporates text from a publication now in the public domain: Rich, Anthony (1849). The illustrated companion to the Latin dictionary, and Greek lexicon. p. vi. OCLC 894670115. https://archive.org/details/illustratedcompa00rich. 

OPER'CULUM (πώμα). A lid or cover for a jar, pot, or other vessel of similar description. (Cato, R. R. 104. Columell. viii. 8. 7.) See the three last illustrations (OLLA, OLLARIUM).

2. Operculum ambulatorium. A sliding or moveable lid, which might be depressed or raised, so as to cover exactly the contents in the vessel it belonged to, like that now used for snuff and tobacco jars. The Romans sometimes covered their beehives with lids of this kind in order that the size of the honeycomb and hive might be exactly proportioned to each other. Plin. H. N. xxi. 47.