72 PROCEEDINGS OF THE MALACOLOGICAL SOCIETT. 



to the umbilical margin ; umbilicus small and deep ; surface polished 

 and bearing numerous obscure lines of growth. Diam. 6 ; alt. 2'5 nun. 



This is a small and delicately formed shell, having a contour very 

 similar to the existing species Vitrca cellaria. The fossil appears to 

 differ from it, however, in its much more depressed spire. Our species 

 is evidently exceedingly rare, as the example described is the only one 

 known to us. 



Formation. — Oligocene (Hcadon Eeds). Localiiij. — Ileadon Hill. 



PTJPA, Draparnaud, 1801. 

 PlTA MULTISriRATA, u.sp. 1*1. YI. Fig. 6. 



Vupa multispirata (Edwards MS.), II. E. jS^ewton. — Syst. List 

 Edwards Coll. British Museum, 1891, p. 273. 



Shell elongate, cylindrical, narrow and turritcd ; spire consisting of 

 six volutions with an obtuse summit ; whorls obtusely angulated at 

 the shoulder, compressed at the sides, and separated by a deep and 

 slightly oblique suture ; the four intermediate whorls increase so 

 gradually that they appear of almost similar size ; aperture perforated, 

 Alt. 5 ; diam. 2 mm. 



These characters are drawn up from a specimen which is merely 

 a cast in calcite, occasioning, of course, some doubt as to its correct 

 generic determination. AYe, however, think it advisable to adopt 

 Mr. Edwards' opinion until more perfect material is obtainable. 

 In the meanwhile we may refer to a cylindrical species of this genus 

 (from similar beds), already described by Edwards as Pupa perdentata, 

 which differs from the present specimen in its greater depth of whorl 

 and much more oblique suture. 



Formation. — Oligocene (Bembridge Beds). Locality. — Headon Hill. 



ISTHMIA,^ J. E. Gray, 1840. 



IsTHMIA DUBIA, U.Sp. PI. YI. Pig. 5. 



Zua duhia (Edwards MS.). Cochlicopa dubia, li. B. Newton. — Syst. 

 List Edwards Coll. British Museum, 1891, p. 274. 



Shell small and tumid ; spire with five volutions ; suture horizontal ; 

 body whorl ventricose and occupying more than half the spiral axis ; 

 remaining whorls gradually increasing, narrow and convex ; apex 

 obtuse ; surface smooth, polished ; aperture semi-oval, perforated, 

 without teeth ; lip unrcfiected. Alt. 3 ; diam. 2 mm. 



We have removed this species from the geniis Cochlicopa on account 

 of its obtuse summit. In some respects it resembles Vertigo Kovi- 

 ffentiensis, described by Sandberger,'^ from the Paris Basin Eocene, 



* Gray's earliest reference to this name occurs in the London Medical Repository, 

 1821, p. 239, where it was used, however, in a trinomial sense {Helix Isthmia 

 cylindrica) and cannot be adopted. The name must date from 1840, when he used it 

 for a section of I'n/ir/o. 



' Laiid-u-Siissw.-i'oucli. Vorwclt, 187-, p. -31, pi. xiii. fig. 22. 



