A (KONTRIBUTION TO THE CENSUS OF THE NON-MARINE MOLLUSCA OF SUFFOLK H. E. J. BIGGS, F.L.S. THE Conchological Society of Great Britain and Ireland (founded 1876) has maintained a census of the non-marine mollusca of the British Isles from its earliest days and the first census report was published in 1885. This was on a county and vice-county basis. T h e last edition, the seventh, appeared in October, 1951, with a Supplement in June, 1966. T h i s basis was found to give a rather inadequate, and in some cases quite inaccurate, picture of the precise distribution of certain species and a much smaller unit of area was necessary. For instance, in East Anglia, Norfolk and Suffolk were each divded into vice-counties, Norfolk East and West and Suffolk East and West, by the meridian of longitude 1° East of Greenwich. Essex was divided by an arbitary line drawn across the county, following certain roads, into Essex North and Essex South. T h e result of this was that on the distrubtion map of a species which had a limited distribution and which lived in a few specially favourable localities, the whole of East Anglia would be blacked in. T o correct this a mapping scheine was adopted in 1962 based on the 10 km. squares of the Ordnance Survey Maps and put undcr direction of Dr. M . P. Kerney of the Imperial College of Science. For the purpose of the new census only records made since 1950 were accepted thus not only would a more accurate knowledge of the distribution of a species be built up but many old records checked and changes in distribution revealed. Some would prove to have extended their distribution, some beeil diminished and others even become extinct. As there are some 3,500 10 km. squares in the British Isles and nearly 180 species of non-marine mollusca on our list the task projected was prodigeous. Iiowever, already, a great n u m b e r of new records have been made ar.d a glance at the most recent map which has been compiled as a result of these new records received up to January, 1968, reveals the following Situation. Ireland has been scarcely touched; Scotland has received a little more attention; Wales and central England only fairly covered. T h e rest of England has had quite appreciable attention. A useful four-page paper has been produced by Dr. Kerney entitled 'Notes for the guidance of recorders' and is available from him to potential workers. In our area of Suffolk, in ordcr to cover the whole county, records must be made for fifty-five squares which lie wholly or in part in the county. Dr. Kerney informs me (in litt.) that he has records of over forty species for only seventeen of these squares and adds 'anything less than this must be considered poor'. In
A Contribution to the Census of the Non-marine Mollusca of Suffolk
Issuu converts static files into: digital portfolios, online yearbooks, online catalogs, digital photo albums and more. Sign up and create your flipbook.