38 PLIOCENE MOLLUSCA. 



Bemarhs. — This form has been reported from time to time under various names. 

 At first Wood referred it to an Eocene species, Belix lenta, Brander, a view 

 adopted by Jeffreys in 1871. Dr. S. P. Woodward identified it, however, with 

 some shells from Bramerton described by his father in 1833, adopting the name 

 of one of them, P. media, and in this he has been generally followed, aslby Wood 

 in 1872, and more recently by Messrs. Kennard and B. B. Woodward. 



Some of the specimens of Vivipara from the Crag were believed by Wood to 

 be specifically distinct from V. media, for example the one figured in his first 

 Supplement (tab. i, fig. 5) as Paludina vivi])ara. This, hoAvever, is regarded by 

 Messrs. Kennard and B. B. Woodward as an immature example of F. media. The 

 latter species is believed by Prof. Sandberger to be related to V. laeta, Martens, 

 from Japan. 



Wood, admitting the resemblance of some of the Crag Paludinse to the Eocene 

 P. lenta, suggests that they may have descended from the latter species. 



Genus VALVATA, Miiller, 1774. 

 Valvata cristata, Miiller. 



1774. Valvata cristata, Miiller, Verm. terr. fiuv. Hist., pt. ii, p. 198, no. 384. 

 1853. Valvata cristata, Forbes and Hanley, Brit. Moll., vol. iii, p. 21, pi. Ixxi, figs. 11 — 13. 

 1862. Valvata cristata, Jeffreys, Brit. Conch., vol. i, p. 74, pi. iv, fig. 9. 

 1879. Valvata cristata, S. V. Wood, Mou. Crag Moll., 2ud SuppL, p. 36, tab. iv, fig. 8. 

 1890. Valvata cristata, C. Eeid, Plioc. Dep. Brit., p. 229. 



1897-1901. Valvata cristata, Kennard and B. B. Woodward, Essex Nat., vol. x, p. 93 et seq., 1897 ; 

 Proc. Make. Soc, vol. iii, p. 201, 1899; Proc. Geol. Assoc, vol. xvii, pp. 226 et seq., 1901. 



Specific Characters. — Shell rather solid, forming a flat coil, concave beneath, 

 closely and regularly striated transversely ; whorls 5, the last very much the 

 largest ; spire flat or slightly concave ; mouth circular ; outer lip thin and 

 somewhat reflected ; inner lip separate from the columella and continuous with 

 the outer lip ; umbilicus large and open, exposing the spire. 



Dimensions. — L. G mm. B. 3 mm. 



Distribution. — Recent : generally throughout the British Islands, and as far 

 south as Corsica and Sicily ; doubtfully recorded from Siberia and Morocco (J. W. 

 Taylor). 



Fossil : Icenian Crag : Bramerton ; Freshwater bed, West Runton. 

 Pleistocene : Barnwell, Barrington, Grrantchester, Woodston, the Fenland and else- 

 where in England. Many localities in British Holocene deposits. 



Pliocene: Monte Mario (Rigacci). Pleistocene: Mosbach; Denmark; Menche- 

 court and Joinville-le-Pont in France. Holocene : Denmark and Sweden 

 (Nordmann). 



