INTRODUCTION. XXXl 
there Planorbis abounds, in company with Limnea stagnalis, 
Limnea palustris, and Bithynia tentaculata, an association 
everywhere indicative of shallow water. I find no Pisidiwm 
in rhines overshadowed by oaks, as near Shapwick station. 
Oaks are uncommon on these moors, which differ from the 
rest of the levels in having plantations here and there of birch, 
alder, Scots pine, spruce and larch. In the plantations near 
Shapwick station I noted the following association : 
Agriolimax agrestis, Linné. 
Vitrina pellucida, Miiller. 
Vitrea crystallina, Miiller. 
Vitrea alliaria, Miller. 
Zonitoides nitidus, JJiiller. 
Arion ater, Linné. 
Arion subfuscus, Draparnaud. 
Pyramidula rotundata, Miller. 
Hygromia hispida, Linné. 
Hygromia rufescens, Pennant. 
Vallonia excentrica, Sterki. 
Helix nemoralis, Linné. 
Cochlicopa lubrica, Miiller. 
Carychium minimum, Miiller. 
Arion ater was a very dark form. The heathland on these 
moors yielded Arion subfuscus, Hyalinia alliaria, and Pyra- 
midulata rotundata. The peat-moors must be a very dreary 
region in winter time. The moors in some parts are often 
under water in flood time, the inhabitants then get about in 
curious flat-bottomed boats or punts, and are sometimes com- 
pelled to enter their homes through the upper windows! 
The monotony of the coast-line of the Levels is relieved in 
the neighbourhood of Weston-super-Mare by rocky headlands 
of Carboniferous Limestone. On the most imposing of these, 
viz. Brean Down, I found the following molluscs : 
Agriolimax agrestis, Linné. 
Vitrea crystallina, Miiller. 
