Members of this family live in tubes made of sand and shell fragments. The head of the worm does not bear a proboscis, but has the mouth at the tip rimmed by some very short tentacles. The body segments lack parapodia and are smooth elongated cylinders. There are a large number of hooked chaetae or bristles on a small pad on the ventral side of each segment. These chaetae have two parallel teeth resembling claws which is a feature that distinguishes members of this family from other polychaetes. The posterior tip bears different appendages in different genera. Family members are unique in having a bell-shaped larval stage known as a mitraria larva. At one time the family was classified as the Ammocharidae.