The collection comprises about 18,000 samples of both dry and alcohol-preserved recent molluscs.
Most recent additions are of non-marine species, particularly terrestrial slugs. Strong points of the collection, derived from our current research, are extensive series of samples from population studies of selected species and numerous captive-reared individuals with known life histories, particularly Deroceras slugs. The majority of the mollusc collection is inventorised in a computer database.

There are also small collections of other invertebrate groups not covered by other departments, mainly
Crustacea, Echinodermata and Cnidaria.