HBLICODONTA LENS 13 



Specific Characters. — Shell minute, smooth, or very finely and regularly striate, 

 smooth at the nucleus, slightly convex above, moderately umbilicate ; umbilicus 

 elongate, rapidly wideniug in the last whorl ; whorls 3 — 3^, quickly increasing in 

 size, the last comparatively large, rounded, expanded towards the mouth ; suture 

 moderate. Mouth somewhat oblique, inclined, forming five-sixths of a circle, sub- 

 angular at the base. 



Dimensions. — Diain. 2*3 mm. by 18 mm. H. 1 mm. 



Dlstrihution. — Recent: Europe and eastern North America. 



Fosdl : Iceniau Crag : Beccles. Pleistocene : Barrington, Cam- 

 forth. Otherwise not yet worked out. 



Remarks. — The specimen here figured was foimd by Mr. A. Bell in a collection 

 of Norwich Crag shells which had been obtained from a well boring at Beccles by 

 Mr. W. M. Crowfoot ; it has been referred by Messrs Kennard and B. B. Woodward 

 to the above species. Some of the localities given for V. puJchelUi may possibly 

 belono- to this shell. 



Genus HELICODONTA, Ferussac, 1820. 

 Helicodonta lens (Ferussac). Plate I, fig. 5. 



1850. Helix lens, Ferussac, Hist. Nat. Moll. terr. fluv., vol. i, p. 110, pi. l.Kvi, fig. 2. 



1854. Helix lens, Eeeve, Couch. Icon., vol. vii (Helix), p. 178, pi. clxxviii, fig-. 1221. 



1884. Helix lens, E. G. Bell, Geol. Mag. [3], vol. i, p. 262. 



1887. Helix lens, Tryou and Pilsbry, Man. Conch., vol. iii, p. 119, pi. xiv, figs. 12 — 14. 



1890. Helix lens, C. Eeid, Plioc. Dep. Brit., pp. 85, 228. 



1899. Helicodonta lens, Kennard iind B. B. Woodward, Proc. Malac. Soc, vol. iii, p. 193. 



Specific Characters. — Shell openly and deeply umbilicate, lenticular, sharply 

 carinated, costulato-striated by the lines of growth; whorls 7, subequal, flattened 

 above, rounded below ; margin of mouth simple, the upper part straight, the 

 dextral and basal part reflected with a small punctiform callus at the superior 

 insertion. 



Dimensions. — Diam. 11 — 13 mm. H. 5 — 6 mm. 



Distribution. — Recent .- Morea and the Grecian Islands (Pfeiffer). 

 Fossil: Waltonian Crag : "Walton-on-Naze. 



Remarks'. — R. G. Bell states that a specimen of a small and not quite adult 

 Helix was found at Walton about 1881 by Mr. Larcher of King's College, London. 

 After a careful comparison with a large series of European Helices in the collection 

 of Mr. J. H. Ponsonby by himself and Dr. Gwyn Jeffreys it was identified as H. lens. 

 Unfortunately, the specimen cannot now be traced. H. lens is a distinctly 

 southern form. The figure here given is that of a Recent shell from Pylos in 



