An extensive group of worms which have the body
covered externally with vibrating cilia. It includes the Rhabdoc/la and
Dendroc/la. Formerly, the nemerteans were also included in this group.
1. A crescent. 2. (Opt.) A lens convex on one side and concave on the other. 3. (Anat.) An interarticular synovial cartilage or membrane; esp., one of the intervertebral synovial disks in some pa...