Spirorbis

Spirorbis is a genus of very small (2–5 mm (0.079–0.197 in)) polychaete worms, usually with a white coiled shell. Members of the genus live in the lower littoral and sublittoral zones of rocky shores. Spirorbis worms usually live attached to seaweeds, but some species live directly on rocks, shells or other hard substrates. Spirorbis was once thought to have a fossil record extending back into the Early Paleozoic, but now all pre-Cretaceous spirorbins are known to be microconchids. The earliest members of genus appeared in the Miocene, but Oligocene finds mayalso be possible. The genus contains the following species: