Kennard 8^ Warren — Tufa Bepont in Totland Bay. 21 



found to be overgrown, but little difficulty was experienced in 

 rfinding a place where the turf had slipped so as to expose the 

 calcareous tufa beneath. Nothing, however, was seen of any of 

 the beds of clay or sand associated with it. The spot from which 

 the present collection was taken was at a very short distance to the 

 -south-west of Widdick Chine, and at about 8 or 10 feet below the 

 top of the cliff. All the shells were obtained from about the same 

 level, within a foot or so, but as no clear section was seen, and the 

 bed collected from may have slipped somewhat from its original 

 level, there is no reason to correlate it with one of the beds of 

 tufa, as described by previous authors, rather than with another. 

 Seventeen species of mollusca were obtained, viz. : — 



Helix Jiortensis (MiilL). 

 CoMicopa lubrica (Miill.). 

 Jaminia muscorum (Linne). 

 Vertigo siibstriata (Jeff.). 



,, piisilla (Miill.). 

 Claiisilia bidentata (Strom.). 

 Carycliium minimum (Miill.). 

 LimncBa truncatula (Miill.). 



Vitrea crysfallina (Miill.). 



„ nitidula (Drap.). 



„ radiatula (Alder). 

 Zonitoides nitidus (Miill.). 

 ^ucomdus ftdvus (Miill.). 

 SpJiyradium edentidum (Drap.). 

 I*yramidula rotundata (Miill.). 

 Helicigona arbustorum (Linne). 

 Helix nemoralis (Linne). 



•It will be noticed that only six of these species have been hitherto 

 ■recorded, whilst several listed species did not occur in the material. 

 Two species, Vertigo siibstriata and V. pusilla, are as yet unrecorded 

 living from the Isle of Wight or Hampshire, though they are known 

 to occur in tufaceous deposits in Hampshire. It is noteworthy that 

 the examples of Helix nemoralis are without bands, whilst the 

 specimens of Helix Jiortensis possess all the bands. Mr. Clement 

 Keid, F.E.S., has noted that in the tufaceous deposit at Blashenvvell 

 a similar state of things occurred.^ The great variation in these 

 species is well known, and this variation is to be found amongst the 

 fossil examples as well as recent, but with the shells from these 

 two similar deposits there is no variation whatever. It affords an 

 extremely interesting problem for which we can offer no solution. 



The deposit lies on an uneven surface of the Potamomya Sands, 

 which underlie the Limneean limestone and belong to the Upper 

 Headon Beds. Both Professor Edward Forbes and Mr. H. W. 

 Bristow describe it as lacustrine, though land-shells are characteristic 

 and fresh-water forms comparatively scarce, as had previously been 

 noticed by Mr. Joshua Trimmer. Both the molluscan fauna and the 

 nature and position of the deposit itself clearly indicate a damp land- 

 surface, over which oozed the water, highly charged with carbonate 

 of lime, which was thrown out of the Headon Hill limestones by 

 springs. It is noteworthy, in this respect, that Mr. Trimmer 

 describes it as being thickest under Headon Hill, and thinning 

 away, and finally disappearing, in a distance of little more than 



1 C. Eeid, "An Early Neolithic Kitchen Midden and Tufaceous Deposit at 

 Blashenwell" : Proc. Dorset Nat. Hist, and Ant. Field Club, 1896, vol. xvii, p. 74. 



