Pisidiums, Pisidium henslowanum, P. subtruncatum and P. milium. The introduced
Zebra Mussel, Dreissena polymorpha, was common.
Terrestrial gastropods that had been drowned during the floods were well represented,
with seven families and eleven species. Particularly interesting is a door snail (Clausilia
sp.). This mollusc is as yet unidentified.
This study has proved very interesting and rich in species, and I will certainly be
repeating it next time there are floods!
List of Species: River Stour. Dedham to Manninatree. 22 & 28 February 2009
Gastropods
Valvatidae
Valvata piscinalis (Muller)
Valvata cristata (Muller)
Planorbidae
Planorbarius corneus (Linne)
Planorbis carinatus (Muller)
Anisus vortex (Linne)
Gyraulus albus (Muller)
Bathyomphalus contortus Linne)
Viviparidae
Viviparus contectus (Muller)
Viviparus sp. (viviparus?) and young
Lymnaeidae
Lymnaea stagnalis (Linne)
Lymnaea auricularia (Linne)
Lymnea peregra (Muller) form ovata Draparnaud
Physidae
Physa fontinalis (Linne)
Physa cf. acuta Draparnaud
Neritidae
Theodoxus fluviatilis (Linne)
Hydrobiidae
Bithynia tentaculata (Linne)
Bithynia leachi (Sheppard)
Hydrobia sp.
12
Essex Field Club Newsletter No. 60, September 2009