128 GUIDE TO THE FOSSIL INVEETEBEATE ANIMALS. 



Gallery edule (N"), Clilamys \Pecten'\ opercidaris (S), Cyprina islandica 

 VIII. ^^-^^ Macoma [Tellina] halthica (N), Mya truncata (N), 

 Scrobimlaria plana (S), Tridonta \Astarte\ ardica (N"), Ven- 

 tricola \_Vemis] casina (S). 

 Central The non-marine series comprises shells of land and 

 Case Al. fresh- water mollusca, found chiefly in river drifts and 

 alluvium. These also are arranged under localities, of which 

 the following are the more important : London and Essex 

 (Fulham, Blackfriars, Admiralty Buildings, Lea Valley, 



Pig. 68. — Shells of Non-marine Mollusca from the Eiver-Drift of the 

 London District. 1, 2, Unio littoralis ; 3, 4, Corhicula fluminalis ; 

 5 , Pisidium astartoides ; 6, P. amniciim ; 7 , Helix fruticum ; 8, Paludes- 

 trina [Hydrohia] marginata. (Lent by Mr. B. B. Woodward ; from his 

 paper in Proc. Geol. Assoc., London, XL, p. 335, 1890.) 



Copford, Walthamstow, Witham, liford, and Grays); Kent 

 (Cray ford 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 amnicum remains ; other extant 

 species are Helix nemoralis, Jaminia [Ptopa] muscomim, 

 Pomatias [Cyclostoma'\ elegans, Bithynia tentaculata, Ancylus 

 fluviatilis, and Neritina Jiuviatilis, among gastropods, with 

 Unio tumidus and Anodonta cygnaea among lamellibranchs. 



