See also: beak. 2. (Arthropoda: Insecta) In Coleoptera, an elevated knob on the humeral angle of the elytra. 3. (Brachiopoda) Apical portion of either valve containing the beak. 4. (Bryozoa: Gymnolaemata) In Cheilostomates, a blunt knob on the front wall of the ovicell. 5. (Mollusca: Bivalvia) That region of the valve surrounding the point of maximum curvature of the longitudinal dorsal profile; when not coinciding with the beak, extending to its base.