• Norwegian: forgjellesnegler


The Caenogastropoda subclass includes the majority of sea snails found in Norway. They usually have two head tentacles and a corresponding pair of eyes. They have only one kidney and one heart chamber. The gills are positioned in front of the heart.


The taxonomy of gastropods are currently under significant revision. The traditional subclass of all gastropods with the gills in front of the heart, called Prosobranchia is no longer valid. In addition to Caenogastropoda, other previous members of Prosobranchia that have become separate subclasses are the top shells (Vetigastropoda) and the limpets (Patellogastropoda).

There are currently some confusion among different sources on how to organize the sea snails. MarBEF - The European Register of Marine Species, are currently (2011) assigning all families to one out of two orders (Littorinimorpha and Neogastropoda), or not to any orders at all. Further genetic studies might lead to further revisions.