The Polychaeta or polychaetes are a paraphyletic cless o annelid wirms, generally marine. Each bouk segment haes a pair o fleshy protrusions cried parapodia that bear mony bristles, cried chaetae, which are made o chitin. As such, polychaetes are whiles referred to as bristle wirms. Mair nor 10,000 species are descrived in this cless. Common representatives include the lugwirm (Arenicola marina) an the sandworm or clam wirmAlitta.