INTRODUCTION. XXXVI 
confined to the limestones of the west. Plate II shews a 
typical haunt of £. montana and associated species. Clausilia 
rolphii (a very rare species) is associated with it on Creech 
Hill near Milton Clevedon. I have noted the same associa- 
tion in the ash-hazel copses of Sussex. H. nemoralis is 
usually associated with the common gorse (Ulex europea, 
Linné), and is fond of climbing the ash saplings; very rarely 
we find H. hortensis with it in the woods, but they are fre- 
quently found together in hedge-banks. 
Before passing on to the consideration of the mollusca of 
the cultivated areas on the limestone, we may note an associ- 
ation which occurs on the natural pastures and _ heath 
pastures of the uncultivated grass-lands. On these the soil is 
usually very shallow, ant-heaps (‘‘emmets’ butts” in the 
present day vernacular, A.S. Emetes’-byht) abound. Dr. 
Moss observes there is frequent and rapid transition of the 
two types, and that ‘even on the natural pasture heather and 
heath plants are frequently found on old ant heaps. . 
Possibly the formic acid of the ants is inhibitive to the 
growth of the limestone plants: and thus the heath plants, to 
whom a sour soil is by no means fatal, are enabled to survive.” 
On the natural pasture we find : 
Agriolimax agrestis, Linné. 
Vitrea nitidula, Draparnaud. 
Pyramidula rotundata, Miiller. 
Helix nemoralis, Linné. 
Helicella virgata, da Costa. 
Helicella caperata, Montagu. 
Jaminia cylindracea, da Costa. 
None in great abundance, and H. nemoralis usually with 
Gorse (Ulex europea). The association appears to be inter- 
mediate between that of the upper woods and the open culti- 
vated pastures. On the heath pasture we have 
Pyramidula rotundata, Mziller (dominant) : associated with 
Limax arborum, Bouchard-Chantereaux. 
