MOLLUSCS 



NON-MARINE 



Although limestones are abundant in the south of the county, there 

 is, on the whole, a lack of calcareous soil in Devon, hence it is by no 

 means a district highly favourable to moUuscan life. Nevertheless, the 

 moist climate and abundance of vegetation (save on the granite uplands 

 of Dartmoor), with the diversified physical features, enable a large number 

 of different molluscs to dwell there. So that, out of some 140 species 

 known to inhabit the British Islands, 109 have been met with in the area. 



Two records, namely those of Helicella itala (the heath snail) and 

 Helix pisana, both cited for Ilfracombe in a local guide to that place, have 

 been rejected as being too doubtful, careful collectors working recently 

 over that district having failed to find them. The latter is a very local 

 shell, which occurs at Tenby and at Swansea on the other side of the 

 Bristol Channel, as well as at Falmouth, Whitesand Bay, and St. Ives, in 

 Cornwall, so that the locality at Woolacombe Sands given for it in the 

 Guide was not an unlikely one, though since it was said to be rare, while 

 the white banded-snail [Helicella virgaia) was common on the spot, it is 

 probable that fine specimens of the latter were mistaken for it, for where 

 Helix pisana does occur it is always present in considerable quantities. 



The lack of any reliable record of the presence of the heath snail 

 (Helicella itala) in the county is remarkable. This mollusc should be 

 sought for especially on the chalk patches between Beer Head and 

 Dorsetshire. Another snail one would expect might be added to the 

 list is Vitrea radiatula, which may be looked for in moss and under decay- 

 ing logs in woods. Of freshwater species noteworthy absentees are 

 Limneea stagnalis, Planorbis corneas, and Bithynia leachii. 



Two importations are worth mention. A single specimen of Helix 

 pomatia, familiarly known as the Roman snail, was picked up beside the 

 Exeter Canal : probably it had been thrown away from some French boat. 

 While the pretty little Opeas goodalli, frequently introduced into green- 

 houses with plants from the West Indies, was very common in Pince's 

 Exeter Nursery in 1850, but according to Parfitt had died out by 1874. 



The most interesting mollusc of those chronicled as inhabiting the 

 county is Hygromia revelata. Like Helix pisana and the Kerry slug {Geo- 

 malacus maculosus) it is one of the rarer and more local of those western 

 species, of which Helicella Barbara and H. virgata are more widely dis- 

 tributed examples, that came to these shores from the Portuguese region 

 along the now submerged plateau connecting these islands with the Con- 

 tinent, which plateau was dry land during a part of the Pleistocene period. 



Another species. Vertigo moulinsiana, is one that had a wider range in 

 Pleistocene times, but has since been dying out, and is now confined to 



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