148 LAND AND FRESH-WATER MQLLUSKS. 
and the west of Scotland. It lives in company 
with Helix virgata and H . caperata, which it ex¬ 
ceeds in abundance. In the marshy grass lands 
of the alluvial plains of Pett and Pevensey 
Levels, in Sussex, B . acutus does not occur ; but 
its usual associates literally carpet the swards 
in many parts; on the other hand, the two 
Helices may be absent, and B . acutus is the sole 
molluscan tenant of the almost barren sandy 
wastes skirting, here and there, our coasts. 
Bulimus montanus —(the Mountain Twist Shell) 
(PI. IX., fig. 81).'—The shell of this species is 
nearly three-fourths of an inch in length, coni¬ 
cal, oblong, semi-transparent, glossy, of a light 
reddish-brown colour, marked with spiral, close- 
set, fine, undulating striae. The spire consists of 
seven whorls; the aperture is about one-fourth 
of an inch wide; the peristome is reflected. 
It occurs in great abundance from April to 
September, associated with B . obscurus, Balea 
fragilis , Clausalia laminata , and Helix lapicida , 
upon the large beech-trees in the woods on the 
oolitic hills of Gloucestershire. It prefers a 
southern aspect, and ascends the trunks of trees 
to heights which render it undistinguishable. 
The beech is an especial favourite with snails, 
more so than any other tree : its smooth bark is 
what they delight in; and after showers the 
trunks may be seen studded with them; the 
