In the animal kingdom, slugs and snails belong in the phylum
Mollusca, a word meaning 'soft animal'. The number of different
species of mollusc varies, according to the source, but is
estimated to vary between 30.000 and 120.000 living species.
Members of the group are found in nearly all available biotopes
on earth. The phylum Mollusca is subdivided into 8 classes.
Except for the Monoplacophora, representatives of all classes
are found in the North Sea. The class Monoplacophora contains
only one single genus (Neopilina ), with a number of species
known from abyssal zones in the Pacific, Atlantic and Indian
Oceans. All other classes will be introduced in separate
chapters in the 'Introduction'. On this CD-ROM, the
classification of the Check List of European Marine Mollusca
(CLEMAN) from the M.N.H.N in Paris is used.