prostomial

from The Collaborative International Dictionary of English v.0.48

Prostomium \Pro*sto"mi*um\, n.; pl. {Prostomia}. [NL., fr. Gr. ?
   before + ?, ?, mouth.] (Zool.)
   That portion of the head of an annelid situated in front of
   the mouth. -- {Pro*sto"mi*al}, a.
   [1913 Webster]