MOLLUSCS (NON-MARINE) That SufFolk, despite the apparent lack of diversity in its physical features and the covering of drift with which the greater part of its surface is masked, is a county favourable to the development of molluscan life is attested by the large number of species that make it their habitat. Not that they are at all evenly distributed. In the middle of the county they are far from abundant, while the Breck district is the poorest. Some species are absent from certain localities while common in others. Thus Hygromia rufescem, one of our commonest snails, is extremely rare in the most easterly part of the county, but common and abundant in all parts farther west. On the other hand Helicella Cantiana (the Kentish snail) is the commonest road-side snail in the east, but rare to the west. While near Mendlesham that agricultural pest, Agriolitnax agrestis, the grey slug, is said to be far from plentiful. Out of the 145 or so species that are known to inhabit the British Islands, no fewer than 116 have been recorded as occurring within the area, and to this number not more than a bare half dozen are ever likely to be added. Four records have had to be rejected. Clausilia biplicata, which appears to have been an error of either observation or determination : Sphaerium rrvicola, which rests on specimens in the Ipswich Museum doubtfully referred to that neighbourhood, though no examples have been met with by recent collectors despite careful search: Pisidium fontinale and P. pusillum, the specimens so named proving on investigation to belong to other species. The Pseudamnicola anatina, recorded from Oulton Broad in 1904 as new to Britain, was considered by Dr. Boettger, who identified it from dead specimens, to be doubtfully distinct from Paludestrina confusa, and Mr. E. A. Smith, I.S.O., of the British Museum (Natural History), after a careful observation of living specimens lately procured from the same spot, states that the mollusc in question cannot be differentiated from the latter form, pointing out in addition that there is considerable doubt as to what shells were meant by the two separate authors who severally employed the trivial name ' anatinus.' Mr. Smith's conclusion has been adopted in the appended list. The occurrences in SufFolk estuaries of the two forms Paludestrina confusa and the recently discovered Assemania Grayana, hitherto known 96
