MOLLUSCS 



NON-MARINE 



The non-marine mollusca are plentifully represented in Kent, the 

 physical features of the county being eminently favourable to their 

 development. 



The terrestrial forms are more abundant throughout the northern 

 portion, or chalk district, than in the sandy and clayey areas verging on 

 the Weald, and find those varied conditions of bare dow^n, or wooded 

 dell and hedgerow, that suit the different requirements of the several 

 species. One of these, Helicella cantiana, takes its name from the county, 

 though this ' Kentish snail ' is by no means confined to this area : it was 

 apparently a late introduction into these islands, for it has not yet been 

 found in any but the most recent post-tertiary deposits. 



The aquatic forms are nearly all present and abound in the numerous 

 ponds and streams as well as in the rivers ; while the salt-marshes and 

 estuaries of the coast provide suitable habitat for the brackish-water 

 forms. 



The literature on the subject is very scattered, and consists mainly 

 of lists relating to isolated localities or notes concerning isolated occur- 

 rences. The most comprehensive paper is that on the ' Land Mollusca 

 of Kent,' by A, Santer Kennard {Kent. Mag. 1896, i. 418). From 

 these sources and the Records of the Conchological Society the sub- 

 joined list has been compiled. 



Of the 139 species occurring in the whole of the British Islands, no 

 less than 1 1 1 may be met with in Kent. Among this number no account 

 is taken of such records as Helix pisana, alleged to have been found near 

 Folkestone, that was most probably only one of the endless varieties of 

 the somewhat similar Helicella virgata. Nor is Clausilia biplicata counted, 

 two examples of which were found in rejectamenta on the shore of 

 Dartford Creek, whither they had probably been wafted by the Thames 

 from some locality much higher up on its course. Still less is any notice 

 taken of the Helix cantianiformis, a name bestowed by a French con- 

 chologist on some unimportant variety of the ' Kentish snail.' Nor has 

 Vivipara contecta been included, though it once swarmed in a pond at 

 Beckenham, since filled in, where it was apparently introduced. 



Three other species occur in post-tertiary deposits of the county 

 that have not yet been met with living in the district, viz. : Vertigo 

 antivertigo, V. pusilla and Succinea oblonga. The first two may have been 

 drifted down to their present place of sepulture, but the last-named was 

 certainly at one time a snail of Kent. 



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