xl MOLLUSCA OF SOMERSET. 
tation of the sandstones and that of the limestones depend 
more upon the presence or absence of humus than upon their 
siliceous or calcareous nature.” 
There are large oak woods in the neighbourhood of Pen 
Selwood, some of these are of ancient character, and are 
possibly vestiges of the ancient forest of Selwood which 
originally covered about 20,000 acres. In these we find : 
Clausilia bidentata, Strém. (dominant) : associated with 
Limax maximus, Linné. 
Limax arborum, Bouchard-Chantereaux. 
Vitrea alliaria, Miller. 
Arion ater, Linné. 
Pyramidula rotundata, Miiller. 
Hygromia rufescens, Pennant. 
Jaminia cylindracea, da Costa. 
Cochlicopa lubrica, Miiller. 
The above association is characteristic of all the oak woods 
on the upper sandstones: in some of the low-lying woods 
Vitrea crystallina, Miller; Euconulus fuleus, Muller ; Vertigo 
pygmea, Draparnaud ; and Carychium minimum, Muller, also 
occur, with Agriolimax agrestis and Agriolimax levis. 
In mixed woods with conifers, on the lower slopes between 
Dunkery Beacon and the village of Luccombe, I noted the 
following association : 
Limax arborum, Bouchard-Chantereaux. 
Agriolimax agrestis, Linné. 
Agriolimax levis, Miiller. 
Arion intermedius, Norman. 
Arion hortensis, Iérussac. 
Pyramidula rotundata, Miiller. 
Helix aspersa, Miiller. 
Helix hortensis, Miiller. 
Clausilia bidentata, Strim. 
Concerning the beech woods on the sandstones in the eastern 
part of the county, Dr. Moss remarks “there is not a natural 
