i9°7- Kknnard. — 0?i VUrea (Hyali?iiaJ hibernica, 327 



to be so. I think that this Irish form may be considered a 

 distinct species. If we are to go on the principle of having 

 as few species as possible, then we ought to consider VUrea 

 htcida, cellaria, helvetica, and alliaria as a single very variable 

 form, but it seems more natural to name the different forms, 

 because we do find that some (e.g. the big cobalt-blue Dra- 

 parnaudi and the common cellaria) are very well fixed. We 

 might now and then find a cellaria with one or more of the 

 characters of D?aparnaudi or of your Irish form, but I do not 

 think that it is at all likely that we should ever come across 

 the complete thing in a community of cellaria" 



It will thus be seen that this Irish shell is unknown on the 

 Continent and is quite distinct from cellaria. Under these 

 circumstances a name is needed, and I would suggest the name 

 of VUrea hibernica, 



Vitrea hibernica, n. sp. 



Shell somewhat convex above, less so beneath, thin, glassy, semi- 

 transparent, pale horn-colour above, clouded white beneath ; striae 

 parallel w T ith the mouth and more pronounced at the suture. Whorls 5-6, 

 body- whorl about half the size of the shell, spire slightly produced, apex 

 blunt, suture shallow and grooved, mouth semilunar and somewhat 

 oblique, umbilicus narrow and deep. Height 6-7 mm. Breadth 11-14 

 mm. It can be distinguished from V. cellaria by the greater height of 

 the spire and by the more oblique mouth : this last being very noticeable 

 in adult examples though less so in immature specimens. (Plate 42, 

 figs. 4-7.) 



There is a small amount of variation in the shell, but most 

 of the examples that I have seen are much higher in the spire 

 than cellatia, and it also attains, as Mr. Adams pointed out, to 

 a much larger size. The largest example I have seen was 

 15 mm. in diameter from Drumcliffe crannoge, Co. Clare (Mr. 

 J. W. Taylor has stated that at Drumcliffe crannoge specimens 

 are said to attain 15 mm. in diameter — Monograph, part 14, 

 p. 31. This statement is only true of one example which is 

 now in the Dublin Museum). Examples are often 7 mm. in 

 height. The highest V. cellaria I have noted is 6*5 mm., 

 though I have examined many thousands of examples. It 

 must of course be admitted that in a highly specialized group 

 like the Vitreas, where the shell is in a degenerate state, there 

 is great difficulty in discriminating between the species on 

 conchological grounds, yet we must not on account of this 



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