Where locomotive appendages (the parapodia of the Polychaeta) exist, they are never jointed, as always in the Arthropoda; nor are they modified anteriorly to form jaws, as in that group.
They are disposed in two groups on either side, corresponding in the Polychaeta to the parapodia; the two bundles are commonly reduced among the earthworms to two pairs of setae or even to a single seta.
Setae always present and often very large, much varied in form and very numerous, borne by the dorsal and ventral parapodia (when present).
It is held, however, that these are a pair of parapodia which have shifted forwards.
The presence of parapodia distinguish this from other groups of Chaetopoda.