Source : Webster's Revised Unabridged Dictionary (1913)

Clitellus \Cli*tel"lus\, n. [NL., prob. fr. L. clitellae a
   packsadle.] (Zo["o]l.)
   A thickened glandular portion of the body of the adult
   earthworm, consisting of several united segments modified for
   reproductive purposes.