Limnea glabra... 
Amphipeplea glutinosa 
Planorbis corneus 
Pialbus. oo 
P. glaber' .:. ise 
P. crista ... ae 
P. carinatus ar 
P. umbilicatus ... 
P. vertex ... ae 
P. spirorbis — 
P. contortus abe 
P. fontanus 
Segmentina nitida (=P. lincatus) 
Physa fontinalis ... 
Aplecta hypnorum 
Paludestrina jenkinsi 
P. ventrosa 
P. stagnalis 
Bithynia tentaculata 
B. ieachii ... hee 
Vivipara vivipara 
V. contecta Bee 
Valvata piscinalis... 
V. cristata sae 
Pomatias elegans... 
Acicula lineata ... 
Neritina fluviatilis 
INTRODUCTION, 
Dreissensia polymorpha ... 
Unio pictorum 
| Cornwall W. 
| Cornwall E. 
Devon §&, 
ww A 
nA WK 
‘a 
wn WK PW 
<< | 
wn 
| Somerset S, 
Be aa | 
MMM KM MM | 
mM | 
4 
Mie MKT = 
MMMM KM KK | 
| 
| Somerset N, 
4 
MM | 
pales Pd Pa Pa 
4 hw KM WM OR Mo HM OM 
‘ 
q 
A 
| 
tes 
ra 
3p 
MM 
LA 
aw 
“4 
— 
