WOODWARD: VITREA ROGERSI. 3II 



(alt. 5*25 mm., diam. max. 9, min. 8 mm.) with higher spire (5^ whorls), 

 is much flatter beneath especially in the region of the umbilicus which 

 is wider; the aperture is smaller for the size of the shell and as a whole 

 directed more downwards than in V. rogersi, while the columellar lip 

 is set more obliquely to the shell axis; it is further less polished on the 

 upper surface while the obscure lines of growth and the puckering at 

 the suture are more marked. The most striking difference, however, 

 is in the rate of increase in the whorls. The relative width of the 

 ultimate to the penultimate whorl, measured radially, is approximately 

 in V. rogersi as 2 to i whereas in V. helvetica it is as 3 to 2. 



Vitrea siibglabra (Bourg.)' is a much larger shell than V. rogersi^ its 

 dimensions being : alt. 6 — 9 mm., diam. 13 — 16 mm., and apparently 

 more like V. helvetica as regards the height of its spire and greater 

 coarseness of its surface. Its author especially contrasts it with the 

 Zonites glaber of Moquin-Tandon and Dupuy, that is to say Vitrea 

 rogersi, he having overlooked their misidentification of the species. 



Of the anatomy of the several species here alluded to nothing can 

 at present be said, but the radulse of V. alliaria, V. rogersi and V. 

 helvetica while closely similar, as was to be expected, in their general 

 aspects present minor differences which support those observable in 

 the shells. Of the two first-named species a small series of radulse 

 are available but of the last only one luckily extracted from the dried 

 up animal in Mr. Ponsonby's specimen. The character of the 

 teeth in the two former series are so constant that it is fair to infer 

 that they are equally so in examples of V. helvetica. The formulae 

 are : — 



11=29 ^i''d about 37 rows. 



11^29 and about 40 rows. 



14=35 ^"d about 45 rows. 

 While the first two species have the same formula the radula of V. 

 alliaria is only two thirds the size of that of V. rogersi, but is propor- 

 tionately to the size of the animal larger. On the other hand V. 

 helvetica which is slightly larger than V. rogersi has a smaller radula 

 with more rows and more lateral teeth in each row. V. helvetica 

 differs markedly from the other two in having no inner cusp on the 

 first admedian tooth. The remaining differences in form between the 

 corresponding teeth in the radulse of these three species will be 

 better gathered from a careful comparison of the figures here given 

 (PI. VL, figs. I — 3) than from any description however lengthy. 



I Bourguignat : "Malac. de la Bretagne," i860, p. 47, pi. i,, figs. 14 — 16. 



A Correction. — In the. Journal of Coitckology, vol. 7, p. 435, Trophon Inin- 

 latus is recorded for Studland Bay. This is an error, the name should be deleted 

 from the list.— J. E. Cooper {Read before the Society, February 11, 1903). 



