I9IO- Stki^fox. — Hyalinia in Ireland. ill 



It is this : that whereas the lines of growth in Hyalinia 

 cellaria and its allies curve in a convex manner (Plate 15, figs. 

 I, 2, 3) as they approach the suture, those of Hyalinia helvetica 

 have a concave appearance (figs. 4, 5). A glance at the 

 accompanying illustrations, which are diagrammatic rather 

 than absolute representations, will give a clear idea of the 

 differences. This is admirably shown in the drawings by 

 Messrs. J. Davy Dean and J. W. Taylor, on Plate vi., vol. 3 of 

 Taylor's Monograph. In addition to this, the sutures of the 

 two shells are different, that of Hyalinia cellaria being much 

 more strongly marked and amounting to a distinct trough. 



In many parts of Ireland Hyalinia cellaria is a woodland 

 species, and has not yet abandoned its primeval surroundings 

 for the neighbourhood of habitations, which as its name almost 

 indicates, is its usual habitat in most countries. The shells of 

 those specimens which live in these shady and moist localities 

 are sometimes very glossy when young, and are more fragile, 

 higher in the spire and therefore narrower in the umbilicus, 

 and finally less clouded w^ith white beneath than those which 

 live in more exposed situations. When full grown this Irish 

 shell is seldom less than from 12 to 14 mm. in maximum 

 diameter, and therefore when only half or three-quarters 

 grown it equals in size an ordinary English or continental 

 specimen of Hyalinia helvetica or H. cellaria. As I think all 

 the species of this genus are in the habit of breeding before 

 their shells have reached full size, it is difficult to saj^ when 

 we are dealing with full-grown shells. I have no doubt how- 

 ever tb.at most of the supposed Irish Hyalinia helvetica could 

 be grown into the normal large form of Hyalinia cellaria 

 commonly met with in Ireland (= Vit7ra hiber7iica, Kennard). 



From its distribution on the Continent, it is extremely 

 unlikely that Hyalinia helvetica would occur in the south- 

 western counties of Ireland and not in the eastern ones, from 

 none of which, though they have been well worked, have any 

 specimens of this shell been recorded. 



References. 



1 J. G. Milne : Contributions towards a list of Irish Mollusca. Journal 



of Conchology, vol. iv., p. 170. 



2 R. A. Phii<i,ips : Hyalinia helvetica. An addition to the Irish Fauna. 



Irish Naturalist, February, 1894. 

 ^ J. W. Tayi.or : Monograph of the Land and Fresh-water Mollusca of 

 the British Islands, Part 14. 



