THE NON-MARINE MOLLUSCA OF THE INTERGLACIAL DEPOSITS

The non-marine Mollusca from the Eemian (Last) Interglacial deposits at Bobbitshole, Ipswich, are analyzed. The fauna is a local one of marsh and fresh-water species and contains very few species which appear to have been washed in from other environments. The more common Mollusca are arranged into groups ofclimatically tolerant, less tolerant and least tolerant species, and the percentage frequency of both species and groups is analyzed through the deposit. Tolerant species dominate in the lower part of the deposit, while the less and least tolerant groups become successively important higher up. A puzzling secondary maximum of tolerant species near the top of the deposit is discussed. The conclusions about local and climatic conditions reached from the Mollusca agree closely with those derived from the plants. It is concluded that the relative abundance of the different species of Mollusca, rather than the presence or absence of isolated specimens of certain species, is important in deducingr the conditions under which they lived.