prostomium
From ZooTerms (Dictionary of Invertebrate Zoology)
prostomium (noun; Greek pro, before; stoma, mouth): 1. The anterior preoral unsegmented portion of a segmented animal's body.
2. An acron.
3. (Annelida: Oligochaeta) The anterior protuberance above the mouth in the first segment; a preoral lobe.
