XXIV MOLLUSCA OF SOMERSET. 
Dupuy; Segmentina nitida, Muller (=Planorbis lineatus, 
Walker); and Paludestrina jenkinsi, Smith. 
We may adopt, as a convenient basis for some comments on 
the ecology of Somerset mollusca, the headings under which 
Dr. Moss has arranged the systems of vegetation of the 
County. 
I LOWLAND AREA. 
A. Coast REGION. 
(1). Muppy Sait Marsn ForMATION. 
(2) Dune ForMATION. 
B. Tue LEVELS. 
(1). AguaTic ForMATION, 
(2). Prat-Moor ForRMATION. 
Il, UPLAND AREA, 
THE DEEP MARLS AND CLAYS. 
THE LIMESTONES. 
THE SANDSTONES. 
O mb 
I LOWLAND AREA. 
Characterised by extensive recent deposits. Mud flats, 
sand hills, alluvium and peat bogs, Dr. Moss observes that 
“the area represents a gain of terra firma, from the sea 
chiefly, by various means of reclamation, and the retention of 
the land is still a matter of difficulty and expense. The area 
is indeed a great monument to the patience, skill and industry 
of the Somersetshire people. The land was primitively tree- 
less. Not a single example of natural woodland occurs, and 
even plantations are uncommon.” The ancient shore may be 
traced here and there many miles inland, the sub-fossil shells 
occurring in it and in the raised beaches, etc., of this area 
have been noted above. 
