What is "prostomium"

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

1870, Latinized form of Greek prostomion "fore-mouth, something before the mouth," from pro "before" (see pro-) + stoma "mouth" (see stoma).

n. (context zoology English) That portion of the head of an annelid situated in front of the mouth.

The prostomium (sometimes also called the acron) is the first body segment in an annelid worm's body in the anterior end. It is in front of (but does not include) the mouth, being usually a small shelf- or lip-like extension over the dorsal side of the mouth.