INTRODUCTION. XXXV 
B. THe LIMESTONES. 
The limestones consist chiefly of large tracts of Carbon- 
iferous Limestone on the Mendips (the slopes of which are 
generally flanked by Dolomitic Conglomerate), and the out- 
crops of Bath Oolite, Coral Rag, Inferior Oolite, Fuller’s 
Earth Rock, Forest Marble, and Cornbrash in the east of the 
county, well shown about Bath and Wincanton. Woods and 
natural copses of ash are very abundant on the slopes of the 
hills. ‘The ultimate or stable plant association on all the 
limestones of Somerset appears to be an ash wood” ( Moss). 
With the ash are associated oak, beech, and horse chestnut, 
in many woods there is a dense undergrowth of hazel, and 
oak, beech, and alder border the streams. The characteristic 
ground vegetation of these woods is large patches of Dog’s 
Mercury (Mercurialis perennis, L.) and Wood Garlic (Allium 
ursinum, Linné). Comparative lists of the ground plants of 
Somerset woodlands may be consulted in Dr. Moss’s paper. 
In the upper woods we have: 
Clausilia bidentata, Strém. (dominant) : associated with 
Limax arborum, Bouchard-Chantereaux. 
Vitrina pellucida, Willer. 
Vitrea cellaria, Miiller. 
Vitrea alliaria, Miller. 
Vitrea pura, Alder. 
Pyramidula rotundata, Miiller. 
Helix fusca, Montagu (rare). 
Helix nemoralis, Linné. 
Jaminia cylindracea, da Costa. 
Cochlicopa lubrica, MWiiller. 
In the lower woods (moist) we have : 
Clausilia bidentata, Strém. 
Vitrina pellucida, Miiller. 
Vitrea cellaria, Miiller. 
Vitrea alliaria, Miller. 
