The Post-Pliocene Non-Marine Mollusca of the South of England

21 3 THE POST-PLIOCENE NON-MARINE MOL LUSCA OF THE SOUTH OF ENGLANn By A. S. KENNARD AND B. B. WOODWARD, F.L.S., ETC" WITH A NOTE BY DR. H. P. BLACKMORE, F.G.S., ETC. [Read Marck ISt, IgOI.] A.-INTRODUCTION. THIS communication is a further instalment of an attempt to place on a more satisfactory basis our knowledge of the geological history of the non-marine Mollusca of this country. It is obvious that if this is done great light will be thrown, not only on geological problems, but also on some of the many vexed questions of geographical distribution. It is, of course, impossible to attempt such a task as we have set ourselves without the aid of numerous friends, and in this respect we have indeed been favoured, and would take this opportunity of thanking those gentlemen who have so greatly and so kindly aided us, either by permitting the free examination of specimens under their care, or by forwarding material for inspection, or in numerous other ways. Those friends to whom we are so indebted are Dr. Henry Woodward, Professor T. Rupert Jones, Dr. Frank Corner, the Rev. R. Ashington Bullen, H. A. Allen, W. J. Lewis Abbott, F. J. Bennett, F. Chapman, R. Miller Christy, Dr. W. H Dall, E. Dixon, R. Elliott, Benjamin Harrison, :Yr. A. C. Hinton, G. Holbrook, J. P. Johnson, J. T. Kemp, A. Loydell, the late C. J. A. Meyer E. T. Newton, w. M. Newton, R. Bunen Newton, H. M Platnauer, R. Nuttall, E. P. Richards, Clement Reid, F. C. J. Spurrell, H. Stopes, D. Taylor, W. A. E. Ussher, and G. White, whilst to Dr. H. P. Blackmore we are indebted for the account of the Holocene deposit at Dewlish. Dr. O. Boettger, of Frank fort, has also rendered us invaluable assistance in determining doubtful examples. We would, however, appeal to the members of this Association for further help. An examination of the localities recorded in this paper shows that the majority are in the county of Kent-in other words, in that part of England which has been most visited by London geologists. There must be numerous other Pleistocene and Holocene deposits in other counties which still await the notice and the pick of the geologist. The district dealt with in the present paper is that lying south of the Thames, and thus includes Kent, Surrey, Sussex, Hamp shire, Isle of Wight, Wiltshire, Berkshire, Somersetshire, Devon and Cornwall. The Holocene deposits are taken first, and then PROC. GEOL. Assoc., VOL. XVII, PART 5, NOVEMBER, 19°1, IS 214 KENNARD AND WOODWARD ON THE POST-PLIOCENE the Pleistocene. In each case the order adopted is to begin with the Thames Valley, treating of the several localities as nearly as possible in the order of their occurrence, proceeding from west to east, and then to deal with the valleys to the south and west, taking them in reverse order, viz., from east to west. Four out of these localities have been touched upon in a former paper, but further facts have come to light since then. The method of procedure adopted, when dealing with published lists of specimens that have since been lost, is to include the several species on the authority of the first recorder, unless there is any doubt as to the correctness of record. In the subjoined table will be found a complete summary of the dis tribution of the various species. In the first column is a complete list of the known species of British non-marine Mollusca, the names of the species extinct in this country being in ordinary type; in the second column those occurring in the south of England are noted; whilst the various fossil records follow in successive columns under the several more important localities. Minor occurrences are grouped together under Holocene and Pleistocene respectively. Finally, in the last column are recorded those species which have been found in the Pliocene beds of England.* A complete bibliography has also been appended. B.-NOMENCLATURE. This not being a systematic paper and the identity of the shell being of more importance just now than the absolute correctness from a " priority" point of view of the name which it is to bear, we have endeavoured to avoid alterations in the nomenclature as much as possible. Undoubtedly, further changes will have, sooner or later, to be made if the rules of zoological nomenclature are to be adhered to ; but these rules, having been founded with the object, as far as possible, of preventing confusion, will, however, we venture to think, be better kept on the present occasion by their breach rather than by their observance. We have, nevertheless, had to accept Pomatias rtjlexus (Linn.), in lieu of Cyclostoma elegans, Miill., and Paiudestrina stagnalis, (Bast.) in place of Hydrobia ulvce, Penn. The greater number of innovations are, however, due to increase of knowledge concerning classification. Thus the great group Helix has been split up by Pilsbry and others into separate genera, while Vertigo edentula has been removed to the Endodontidre, and as Sphyradiutll edentulum ranks next to Punctum pygmo:um. • The Forest Bed being now generally beld to belong to the Pleistocene period, all reference to species occurring therein is omitted from this column, NON-MARINE MOLLUSCA OF THE SOUTH OF ENGLAND. 215 A conspicuous alteration due in part to priority and in part to anatomical investigation, is the substitution of Helicella barbara (Linn.) for the time-honoured Bulil1lus acutus, Mull. Other transmutations are due to errors of identification, viz. : Hygromia granuiata, Alder, is not, as had been supposed, the Helix sericea, Drap.; Cochlicopa lubrica, Miill., is not the Helix subcylindracea, Linn.; nor is Planorbis glaber, Jeff., identical with P. parous, Say, as we have had previous occasion to point out. Vitrea j?,labra, we have been constrained to leave as of " Brit. Auct.," since it has still to be satisfactorily identified, or named. It is certainly not the Vitrea glabra (Stud.) Charp., and differs considerably from the V. Helvetica, Bourg. C.-HOLOCENE DEPOSITS. I. Newbury. The first published notice of the Mollusca from the Kennett Valley deposits at Newbury was in 1854 (9), when Professor T. Rupert Jones recorded fifty-one species on the authority of Mr. J. Pickering. In 1856, Mr. S. V. Wood noted forty-five species (14), none of which were new, the printer, perhaps, being respon sible for the omission of the rest. The first list was copied with a fewalterations in nomenclature in 1872, in the Geological Survey Memoir (31). In 1883, one of us pointed out that the examples of Helix aspersa, recorded from the Newbury marl, were probably of quite recent date, since the numerous pits which from time to time have been dug in the peat quickly fill up (Science Gossip, 1883, pp. II5, 237), and Dr. Frank Corner informs us that Saxon remains have been found at a depth of 10 feet in the peat; whilst in 1897, an account of the Mollusca was given by us as an appen dix to a paper by Mr. E. Percy Richards (65). Of existing examples there is a series at the Natural History Museum, which had been presented by Mr. Pickering to this Association, and transferred by them to the national collection. This has been supplemented from a series in our own possession. We are thus enabled to compile a list of forty-four species, nine of which have not previously been recorded. We have considered it advisable to reject five records as being, in all probability, errors in identi fication. These are, Limax carinatus [= Amalia sowerbyi], Zonttes [= Vz'trea] aliiarius, Helix hortcnsis, Helix [= Helicella] virgata and Vertigo alpestris. Two of Mr. Pickering's species are now considered as only varieties of other forms. We have hitherto rejected Helix asperse, but on further consideration we have decided to include it on the authority of Mr. Pickering. As we have already seen, it has been found in an 216 KENNARD AND WOODWARD ON THE POST-PLIOCENE undisturbed Neolithic deposit at Greenhithe, and it has also been found in the Lea Valley (Essex Naturalist, 1897. Vol. X., p. 92). The new records are :-- Vitrea nitida, Vertigo anthJcrtigo, Arion ater, Planorbisgiaber, Helice/la itala, PI1)'sa ltypnorulIl, Helicigona lapicida, Pisiditon milium, " nitidum, Nine other species we have tabulated on the authority of Mr. Pickering, thus bringing the total up to fifty-two. Of the new records, by far the most interesting is PisidiuJII milium. It has been found in the Forest Bed and in the Pleistocene of Ilford, but has hitherto been unknown from any deposit of later age. At the present day it is a local form, though widely distributed throughout England and Scotland and even met with in the Orkneys, In Wales it is only known from Anglesey, and in Ireland it has been noted from Galway. It is, of course, very improbable that so widely distributed a form should be a modern addition to our fauna, and its occurrence in tbe Newbury deposit is a welcome proof of this view. Planorbis glaber is an extremely rare form in Holocene deposits, having only been found at Westminster, though it is a common Pleistocene species. In studying the shells from this locality we have realised how necessary it is, in order to ohtain an accurate idea of the fauna of any alluvial deposit, not only to have a large quantity of material, but also to obtain it from as many sections as possible. Our collection was derived from three sources. Firstly, a series col lected by one of us during an excursion of this Association to Newbury in 1879 j secondly some specimens sent by Mr.

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