252 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



experienced by recent collectors. Its occurrence in rain-washes at 

 Cuxton and Greenhitlie, Kent, and in the Neolithic flint mines at 

 Grimes Graves, Weeting, Norfolk, clearly show that this species 

 was able to live at one time on what is now dry chalkland. 



Besides these species there are several other forms whose area 

 of distribution has slightly diminished. Helicodonta obvoluta (Mlill.), 

 from its occurrence in the Neolithic flint mines at Cissbury 

 {ArchcEologia, vol. xlv, 1880, p. 339), had formerly a more easterly 

 distribution in Sussex. 



Helix pomatia, Linn. , occurred at Northfleet, Kent, in association 

 with Roman remains, and in a pre-Roman rain- wash. It is quite 

 absent frorn the district at the present time, but probably intensive 

 cultivation will account for this. So far nothing has been found 

 enabling us to link up the two areas of distribution in Kent. 



The only Holocene record for Succinea ohlonga, Drap., is at 

 Harlton, Cambridgeshire, a county in which it has not yet been 

 detected living, whilst Clausilia rolphii, Gray, though unknown 

 living in North Essex, occurs fossil at Copford and Felstead. 



It will be noted that nearly all the species whose area of distribu- 

 tion has diminished are damp-loving forms, and it may be urged 

 that this is the result of human agehcies in draining the swamps 

 and marshes, and thus decreasing the natural habitats. The 

 deposits yielding these species, however, are not confined to the low- 

 lying grounds, but occur on the slopes of the chalk hills well above 

 the springs, and where the influence of man cannot be traced. 

 Thus at Cuxton, Kent, Helicella radiatula (Aid.), Arianta arhustorum 

 (Linn.), Lauria cylindracea (Da Cost.), Vertigo suhstriata, Jefi., and 

 Acicula lineata (Drap.) occur in a Neolithic deposit, but do not 

 occur on these same dry slopes at the present time. Moreover in the 

 same deposit the form of Fruticicola [Capillifera) hispida (Linn.), 

 difiers markedly from the chalk-hill form, the var. nana, Jeff., which 

 is now living there. At Totland Bay (Isle of Wight), Blashenwell 

 (Dorset), at Caerwys (Flintshire), and Leckwith (Glamorganshire) 

 this damp-loving fauna is found in tufa which has long ceased to 

 form, and in the case of Blashenwell the tufa is certainly Neolithic 

 (C. Reid, Proc. Dorset Nat. Hist, and Antiq. Field Club, vol. xvii, 

 1896, pp. 67-75). Wherever it is possible to date these deposits by 

 archaeological evidence the result is always the same, that they are 

 early Holocene, when human activities were negligible, and the 

 conclusion is inevitable that at one period, at least, formerly the 

 rainfall of England must have been much greater than it is to-day. 



Besides the presence or absence of certain species, there is another 

 important series of facts the full significance of which cannot yet 

 be ascertained, and that is the varying development of the 

 individual. It is easy enough to conceal our ignorance by using 

 such phrases as " suitable conditions " or " congenial environment ", 

 but the fact remains that we know next to nothing of the multiple 



