annulus
From ZooTerms (Dictionary of Invertebrate Zoology)
annulus (noun; plural annuli, annuluses; Latin annulus, ring): 1. Any ring-like circling of a joint, segment, spot or mark.
2. (Bryozoa: Phylactolaemata) The outer epidermal layer of a statoblast that encircles the protective capsule.
3. (NEMATA) The interstice area between the transverse striae of the body cuticle.
