356 



ON THE OCCUEEENCE OF FLANORBTS TORTICULUS, TROSCHEL, 

 IN THE PLEISTOCENE OF ENGLAND, WITH NOTES ON SOME 

 OTHER PLEISTOCENE MOLLUSCA. 



By A. S. Kennard and B. B. Woodwaed, F.L.S., F.G.S. 



Read 16th June, 1905. 



When engaged in working out the very large series of moUuscan 

 remains obtained from the 100 feet terrace of the Thames at Swans- 

 comb, several immature examples of Planorhis were noted, which we 

 could not associate with any recent English species, and we are again 

 indebted to Dr. A. C. Johansen for identifying the form as Planorhis 

 rorticulus, Troschel, a species which had not hitherto been detected in 

 these Islands, either fossil or recent. Since then we have recognized 

 it as occurring in two other Pleistocene deposits, viz., the brickearths 

 of Grays, Essex, which j'ielded a single example, and the well-known 

 deposit at West Wittering, whence three or four specimens have been 

 collected. We have so far failed to trace it from any other locality. 

 On the Continent it has been recorded fossil from the Pleistocene of 

 Weimar, Burg, and Graf en in Thuringia by Dr. E. W. Wiist,^ and 

 from the Holocene (oak period Neolithic) of Refsnoes and Kareboek in 

 Denmark by Dr. A. C. Johansen,^ and we are informed by Dr. Johansen 

 that it occurs in deposits of the same age in Scandinavia. 



It is found living at Malmo according to Westerland, whilst Jordan^ 

 records it as P. acies, Miihlf., from Holland, middle Germany, south- 

 west Germany, Switzerland, and north Italy. 



The species is an extremely interesting addition to what may well 

 be termed the old Thames-Rhine fauna. In this country one first 

 recognizes this group of mollusca in the Norwich Crag, where 

 Corbicula fiuminalu occurs. It is quite possible that Vivipara media 

 and Paludestrina Reevei also are members, but of this fact no con- 

 firmatory evidence is yet forthcoming. In the newer Weybourn 

 Crag we meet^ with Lithoglyphus fuscus and Vivipara glacialis, whilst 

 in the Forest Bed there are five fresh forms which can be referred to 

 it — JSematurella Rimtoniana, N. aUnostoma, Valiata fluviatilis, Pisidium 

 astartoides, and P. supimim. In the Pleistocene of the 100 feet 

 terrace of the Thames at Swanscomb we have the additional forms 

 of Vivipara diluviana, Neritina Grateloiipiana, Planorhis vorticulus, 

 and Valvata pisctnalis, var. naticina, whilst in the still newer 

 Pleistocene of Grays one notes Pisidmm amnicum, var. Danuhialis. 



' E. Wiist, 1901, " Untersuchungeu iiber das Phozan und das alteste Pleistozan 

 Thiiringens " : Abhandl. Gesell. Halle, xxiii, pp. 218-248. 



2 A. C. Johansen, " Om den Fossils Kvartajie Molluskfauna i Danmark " : Copen- 



hagen, 1904, p. 66. 



3 Nova Acta Acad. Cses. Leop. -Carol. Nat. Cur., vol. xlv. No. 4, 1883. 



