236 



NOTE ON THE OCCURRENCE OF PLANORBIS STROEMII, 

 WESTERLUND, IN THE HOLOCENE DEPOSITS OF THE 

 THAMES VALLEY. 



By A. S. Kennard and B. B. Woodward, F.L.S., etc. 



[Abstract.] 



When sorting out material from the holocene deposits at Walthamstow, 

 Mr. A. S. Kennard was struck by the abundance of a form of Planorbis, 

 which differed so distinctly from its congeners, not only in form and 

 sculpturing, but also in its fossilization, as to be readily and easily 

 separable from them. This form was identical with that noted by 

 Mr. B. B. Woodward from Westminster and Kew as a keel -less form of 

 P. carinatus 1 The authors have traced it, in their own collections and 

 those at the Natural History Museum, from the dried " Thames Mud " 

 of the Embaukment on the site of the New Scotland Yard ; from the 

 holocene gravels of the same spot and from the Houses of Parliament ; 

 from Betteridge Road, Fulhain ; Kew ; Staines ; the Lea Valley ; and 

 Clifton Hampden, Oxfordshire. 



Mr. A. C. Johansen, of the Zoological Museum, Copenhagen, then 

 most obligingly showed the authors specimens of the same shell 

 obtained by him in a subfossil state from the banks of the Thames 

 between Kew and Richmond, at a point exactly opposite Sion House. 

 Mr. Johansen recognized it as identical with P. Stroemii, Westerl., 

 a form now living in Siberia, Finland, aud Northern Scandinavia, 

 while it occurred in Denmark, he stated, solely in deposits of the 

 Oak period (= Bronze Age). 



The authors were of opinion that this form was a valid species and 

 might prove to be identical with the Helix Draparnaiidi of Sheppard, 

 and gave reasons for this inference. 



1 Troc. Geol. Assoc, vol. xi, pp. 339, 340. 



