• Webster's Revised Unabridged Dictionary
    • n Metastoma (Zoöl) A median elevation behind the mouth in the arthropods.
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Century Dictionary and Cyclopedia
    • n metastoma In Crustacea, a median development, often bifid, of the ventral part of a somite immediately behind the mouth. It is the so-called labium or under lip, composed of small pieces immediately below or behind the mouth. Also called hypostoma. See the quotation, and cut under cephalothorax.
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Webster's Revised Unabridged Dictionary
NL. metastoma, from Gr. meta` behind + sto`ma mouth