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n. pl. pro·sto·mi·a (-mē-ə)
The anterior portion of the head of an annelid worm, situated in front of the mouth.

[New Latin, from Greek prostomion, mouth, lips : pro-, in front of; see pro-2 + stoma, mouth.]

pro·sto′mi·al (-əl) adj.


n, pl -mia (-mɪə)
(Zoology) the lobe at the head end of earthworms and other annelids: bears tentacles, palps, etc, or forms part of a sucker or proboscis
[via New Latin from Greek prostomion mouth]
proˈstomial adj


(proʊˈstoʊ mi əm)

n., pl. -mi•a (-mi ə)
a small protuberance from the first segment above the mouth in certain worms and mollusks.
[1865–70; < Greek prostómion mouth. See pro-2, stoma, -ium2]
pro•sto′mi•al, adj.