The majority of species of the Order Cephalaspidea have a small bubble-shell with truncate or involute spire and these shells alone have been in many cases the only source of information to describe species. Because of the extreme similarities of these shells there are extensive taxonomic confusion within the group and the Scandinavian region is no exception. This project aims to study the diversity of cephalaspids in the North-east Atlantic with emphasis of the Scandinavian peninsula. The taxonomy of species will be revised by shell morphology, fine-scale anatomical dissections using light and scanning electron microscopy and molecular systematics.