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CONTRIBUTIONS TOWARDS A 

 LIST OF WEST-SUFFOLK NON-MARINE MOLLUSCA. 



By a. MAYFIELD. 



(Read before the Society, November 8th, 1905). 



In the last edition of the " Census of the British Land and Fresh- 

 water, MoUusca " only eighteen species are recorded from West 

 Suffolk. In the hope that, with the publication of the next edition 

 of the "Census," vice-county 26 may appear less of a "dark corner," 

 I have compiled the present list and forwarded the shells collected 

 to the Society's referees. 



For the purpose of briefly describing the soils and sub-soils, West 

 Suffolk may be conveniently divided into four nearly equal parts, by 

 two lines : one drawui longitudinally from Thetford to Sudbury ; the 

 other at right-angles to the former from Newmarket to Stowmarket. 

 Of these four divisions, the north-east (i), south-east (2), and south- 

 west (3), are mainly agricultural, and the land-molluscs inhabiting 

 them chiefly of the hedgerow-loving kinds. The aquatic species are 

 those preferring the ponds, ditches, and other small bodies of water. 

 In the two eastern divisions (i and 2) the chalk (which forms one 

 continuous stratum under the whole of the vice-county) dips toward 

 the south-east, producing a gradual change southwards and eastwards 

 from light lands upon a subsoil of chalk to heavy lands upon a sub- 

 soil of yellowish-grey clay overlying the chalk. 



In the south-west division the chalk is covered with layers of sand, 

 gravel and brick-earth. Here is the highest ground of the county, 

 viz., a tableland lying to the south-west of Bury St, Edmunds, the 

 most elevated spot being mid-way between the villages of Rede and 

 Depden, where the elevation reaches 420 feet. This district is, or 

 was, the home of Ena moniana. 



In the north-western division (4) are two distinct districts widely 

 diff'ering from the agricultural lands already mentioned. In the 

 extreme north-west there is a tract of fen-land, called the Mildenhall 

 Fen, varying from two to about twenty feet above sea-level. Here all 

 the more common aquatic species are abundant. East of this fen is 

 another tract of level ground, with an average elevation of 150 feet. 

 Here the chalky subsoil is thinly covered with sand. In a few places 

 agriculture is attempted, the areas broken up for this purpose being 

 called " brecks," on account of which the whole district is known as 

 the " Breck District." For miles, however, the land is solely occu- 

 pied by rabbit-warrens, covered with short grass, moss, and bracken. 

 A peculiar feature of the Breck district is the occurrence of wild 

 plants, insects, and birds, which are usually to be met with only upon 



