THE NON-MARINE MOLLUSCS OF ESSEX.
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Order—PROSOBRANCHIATA.
Sub order—MONOTOCARDIA.
(a) taenioglossa.
Family—Hydrobiidae.
Genus—PALUDESTRINA, D'Orbigny, 1840.
Paludestrina confusa, Frauenfeld (=Hydrobia and Bythinia
similis, Draparnaud).
A.—Becton ; (Jenkins).
Paludestrina jenkinsi, Smith.
A.—Becton ; (figured E.N., vol. iv., p. 213) : Becton ;
Coldharbour Point ; (Jenkins) : *Rainham ; (Jenkins'
Coll.) : Tilbury ; (Horsley).
Paludestrina ventrosa, Montagu.
A.—Coldharbour Point to Tilbury Fort ; West Tilbury ;
(Jenkins) : Thurrock Marsh ; (Jenkins Coll.) : Tilbury ;
(Horsley): Grays; Tilbury; (British Museum).
B.—Between Walton and Thorpe-le-Soken ; (specimens col-
lected by J. C. Shenstone—W.M.W.) : St. Osyth ;
(E.N., vol. v.,p. 259); *Clacton; Witham; (British Museum).
C.—Saffron Walden ; (S.W. Museum) : Harwich ; British
Museum).
Paludestrina stagnalis, Baster (=ulvae, Pennant).
A.—Grays ; Tilbury ; (Jenkins).
B.—Wyvenhoe ; (British Museum) : *†Colchester ; (Laver
Coll.); Clacton ; (K. and W.).
[Paludestrina marginata, Michaud.] Extinct in Britain.
A.—Grays; (British Museum).
B.—Copford; (British Museum) : *Clacton; (Webb, 4).
Genus—BYTHINIA, Gray, 1821.
Bythinia tentaculata, Linne.
A.—River Stort ; (Ingold): River Lea, Chingford ; (C.S.R.;
Scharff) : River Roding, Woodford ; (C.S.R., Old-
ham) : Wanstead ; Fern Hall; Barking Side ; Roding
Meadows ; St. Swithin's Farm ; (Crouch) : Coldharbour
Marsh—and white variation ; (Jenkins) : Canning Town ;
(K. and W.): Ilford; Walthamstow; (British Museum):