sulcus
From ZooTerms (Dictionary of Invertebrate Zoology)
sulcus (noun; plural sulci; Latin sulcus, furrow): 1. A furrow, groove or fissure.
2. (Arthropoda: Insecta) A suture formed by an infolding of the body wall. See also sulci.
3. (Brachiopoda) The major depression of the valve surface, externally concave in transverse profile and radial from the umbo.
4. (Cnidaria: Anthozoa) A groove leading into the gullet
See also: siphonoglyph. 5. (Mollusca: Bivalvia) The radial depression of the shell surface.
