Nudibranchs belong to a class of molluscs called the gastropods,
this class is divided into three subclasses; the prosobranchs (eg. the common whelk, the periwinkle and the limpet);
the pulmonates (air breathing snails and slugs, eg. garden and pond snails and slugs) and the opisthobranchs (commonly
know as sea-slugs). Both the opisthobranchs and the pulmonates are descendants of the prosobranchs.
Nudibranchs are opisthobranch molluscs in which the adult stage has completely lost
both the shell and operculum. They share this character with the plant-eating sacoglossa or ascoglossa, which are
not covered here. The loss of the shell has allowed a diverse array of body forms within this order. The Nudibranchia
is divided into the following four suborders; the Dendronotacea, Doridacea, Arminacea and Aeolidacea. http://www.pictonb.freeserve.co.uk/nudibranchs/contents.html
For further references on Nudibranchs, consult the web sites below.
http://slugsite.tierranet.com/
http://www.eeph.com/~queue/nudibranch.html
http://www.xinit.se/~jor/dive/nudi/
For more information see