- Norwegian: kjeglesnegler
The main characteristic of the top shells is the microscopic shell structure. In a microscope the shell appear to be build from oblong plates intersecting each other in a very regular pattern.
The shells range in size from 2 mm to 30 cm. Some are turret-shaped, others coned or almost spherical. The opening is usually oval and many species have a lid, operculum, they can use to close it. There is usually a distinct snout containing the mouth.
The top shells were formerly regarded as members of the subclass Prosobranchia that included all gastropods with the heart positioned in front of the gills. Prosobranchia is now replaced by three subclasses, where the top shells constitute one, Vetigastropoda. There are currently a total of eleven superfamilies in this subclass.