\Ch[ae]*top"o*da\, n. pl. [NL., from Gr. ? hair +
-poda.] (Zo["o]l.)
A very extensive order of Annelida, characterized by the
presence of lateral set[ae], or spines, on most or all of the
segments. They are divided into two principal groups:
{Oligoch[ae]ta}, including the earthworms and allied forms,
and {Polych[ae]ta}, including most of the marine species.