Linked from
The 7 pages that link to Clitellum, each with the reason it gives.
AnnelidaBroader topic: Its presence identifies the major group containing earthworms and leeches.
OligochaetaRelated: Its presence is a conspicuous feature of earthworms and other oligochaetes.
TubifexRelated: In mature Tubifex, this reproductive structure helps form a cocoon for eggs.
Giant Gippsland earthwormRelated: The adult worm uses this structure to form a cocoon for its eggs.