The Collaborative International Dictionary of English v.0.48:

Praeoperculum \Pr[ae]`o*per"cu*lum\, n. [NL.] (Anat.)
   Same as Preoperculum. -- Pr[ae]`o*per"cu*lar, a.
   [1913 Webster] Praescutum
   Praescapula
   Praepubis
   Praeoral