128 GUIDE TO THE FOSSIL INVEHTE15RATE ANIMALS. 
Gallery cihdc (N), Chlamys {Pcctcn] opercularis (8), Cyprina islandim 
VIII. Macuma \Tdlina\ halthica (N), Mya trvncata (N), 
Sayhmdaria 2 d(ina (8), TridoiUa [Astarte] arctica {^), Vcn- 
tricola \ Fenuft] casina (8). 
Central The non-marine series coinprises sliells of laml and 
CaseAl. fi'esh-water inollusca, found chiefly in river drifts and 
alluvium. These also are arranged under localities, of which 
the following are the more important: London and E.ssex 
(Fulham, Blackfriars, Admiralty Buildings, Lea Valley, 
Fig. 68.— Shells of Non-marine Mollusca from the Eiver-Drift of the 
London District. 1, 2, Unto littoralis ; 3, 4, Cmhiciila fluminalis ; 
5,Pi^idiiimastartoides ; 6,P.aninicum ; 7, J/cZiaj/rMiicMw; S, JV/ZaJes- 
trina [Hydrobici] marginaUi. (Lent by Mr. B. B. Woodward ; from his 
paper in Proc. Geol. Assoc., London, XI., p. 335, 1890.) 
Copford, AValthamstow, Witham, Ilford, and Grays); Kent 
(Crayford and Crossness) ; Cambridgeshire (Barnwell and 
Barrington). Most of the species still live in England, but 
a few are altogether extinct. Thus of those depicted in 
Fig. 68 only Fisidium arrmicum remains ; other extant 
species are Helix ncmoralis, Jaminia [/•’ttjoa] m%Lscorum, 
Foviatias [^Cyclostoma^ elcgans, Bithynia tcntaculata, Ancylus 
JluviatUis, and Neritina Jluviatilis, among gastropods, with 
Unio tumidus and Anodonta cyynaea among lamellibranchs. 
