THE NON-MARINE MOLLUSCA OF SUFFOLK I. J. KILLEEN
The interest in the non-marine Mollusca of Suffolk has a history going back to the early nineteenth Century. In 1823 Revett Sheppard, a local parson, published an account of land and freshwater shells including a list of Suffolk species. There followed a gap until 1891 when C. Greene published a catalogue of the Land and Freshwater Shells of Suffolk. In the ensuing years several accounts on Suffolk Mollusca by Arthur Mayfield appeared in the Journal of Conchology. Continued interest by local naturalists, notably G. T. Rope, C. Morley and C. G. Doughty culminated in a summary of the Mollusca of Suffolk by Morley in 1938. Apart from a few short notes in these Transactions very little work was carried out in the county for the next 30 years. In 1961 the Conchological Society of Great Britain and Ireland instigated a national survey based on the 10km grid squares of the Ordnance Survey. So far as Suffolk was concerned, the vast bulk of the recording for this project was carried out between 1967 and 1974 by visiting members of the Society with some assistance from local naturalists. The results of this survey were published as an Atlas of the Non-Marine Mollusca of the British Isles (Kerney, 1976a). Recording has continued Over the last 10 years and a second edition of the Atlas is planned for the near future. Several interesting distribution patterns emerged from this survey, reflecting physical effects such as geology and climate. However, at county or vice-county levels, the 10km Square is a rather coarse mapping unit. It has become usual for the 2 X 2km Square, or tetrad, to be used as the unit for recording at county level. This enables a more precise method of showing the distribution of a species within a given area. Several tetrad atlases have already been produced in many counties, particularly for flora but also other groups, e.g. The Non-Marine Mollusca of the Isle of Wight (Preece, 1980) and most recently for Butterflies in our own county (Mendel & Piotrowski, 1986). In 19801 embarked on a survey to record the mon-marine Mollusca of the county, i.e. East Suffolk (v.c. 25) and West Suffolk (v.c. 26), using the tetrad grid system. To date (January 1986) some 600 tetrads have been investigated. The attached map shows the coverage and number of species from each tetrad. Even with 60% coverage many distinct distribution patterns are emerging. Furthermore, incorporation of old records has revealed that many species are declining or are on the verge of extinction in Suffolk. A major factor responsible for these declines is the loss of habitats such as rieh wetlands and chalk grassland. DĂźring the course of the present survey several species previously unrecorded in v.c. 25 and 26 have been discovered:
Trans. Suffolk Nat. Soc. 22