INTRODUCTION. XXX1X 
Helicella caperata, Montagu. 
Hygromia rufescens, Pennant. 
Hygromia hispida, Linné. 
Cochlicopa lubrica, Miiller. 
H. virgata, H. itala, and H. caperata are the dominant 
species on dry upland calcareous pastures. Forms with well 
developed dark bands predominate. It is supposed that this 
type of banding is protective, serving to make the shell easily 
visible to sheep. Indistinctly marked and light unicolorous 
forms are not so easily seen, and are often eaten. 
Cecilioides acicula, Miller, a truly subterranean species, 
respecting the habits of which little is known, is abundant in 
some districts on the Oolite, judging from the numerous shells 
washed from the soil during heavy storms. I have never 
found it alive. It is probably gregarious ; after floods I have 
seen in quarries about Wincanton, the high-water mark indi- 
cated on the side of the quarry by a narrow white zone of 
thousands of dead shells. Its occurrence in burial places has 
been noted in many parts of Britain, including Somerset 
(p. XV1). 
C. THE SANDSTONES. 
The sandstone areas of Somerset occupy much of the highest 
land in the county, and comprise, geologically, the Devonian 
with Old Red Sandstone, Coal Measures, Upper Greensand, 
and Chalk. The Devonian tracts of Exmoor culminate in 
Dunkery Beacon, 1,707ft., the highest point in the county. 
The Old Red Sandstone is exposed on the top of Mendip, 
highest point Blackdown, 1,008ft., and in certain other locali- 
ties in the north-west, where the Carboniferous rocks have 
been worn away. The Upper Greensand occurs in the eastern 
part of the county, bordering on Stourton and Kilmington 
(Wilts), the highest point is King Alfred’s Tower, 850ft. 
There are small chalk areas in the neighbourhood of Crewkerne. 
Dr. Moss is of opinion “ that the differences between the vege- 
