THE ASSOCIATION OF HELIX NEMORALIS 

 AND H. HORTENSIS IN IRELAND. 



By R. welch. 



(Read before ihe Society, December lo, 1902). 



Helix neinoralis is a common S])ecies in almost e\'ery county in 

 Ireland. H. horte/isis, on the contrary, is very local and usually rare. 

 In the four localities in which I have found the latter the geological 

 formation differed very much. Quartzites in N.\V. Donegal (Port- 

 salon), Ordovician (really capped with Boulder Cla}) in Co. Down 

 (Downpatrick), and Carboniferous Limestone at Ardbraccan, near 

 Navan, and Kells, both in Co. Meath. 



1. Portsalon. — B. hortensis is excessively local in a damp ditch 

 with a hedge above it. The molluscs shelter in the damp grass roots 

 of the ditch in dry weather, in wet, swarm all over the hedge. I saw 

 no H. neinoralis with them on any of my visits, nor did I see any li. 

 hortcnsis with the former which are plentiful all over the sea-bluffs, not 

 more than 200 to 250 feet away, with Helix aspersa. H. hor/e/isis 

 does not seem to spread to the adjoining dunes with their short turf, 

 while H nemomlis does, the latter being a sand-dune species in 

 Ireland or very largely so. 



2. Downpatrick. — Both species occurred together in the 

 cathedral graveyard. H. horknsis is very rare outside, but predominates 

 inside the walls. I only found two forms at any time, 12345 and 

 00000, both var. libelliela, with an occasional tendency to i234S- O'l 

 approaching dry weather //. liortensis seems to hurry to damp shelter 

 more quickly than the other species. 



3. Ardbraccan. — Old graveyard, near Navan, Meatii. H. lior- 

 tensis swarms here in wet weather all over the tombstones and 

 rank vegetation, with a few of the other species. In dry weather 

 not a trace of it is to be found unless after careful search in damp 

 corners, at bottom of tombstones and grass roots, etc. I agree with 

 Mr. Pearce that where one species is plentiful the other is rare or 

 absent and I only know one place in Ireland (Maghery, W. Donegal) 

 where a hybrid race may possibly be present, though I doubt even 

 that. The plentiful food supply and moisture of these old Irish 

 graveyards seems to suit H. hortensis very well. H. neinoralis can 

 exist in much dryer and less sheltered situations, even on our wind- 

 swept dry dunes, where H. hortensis does not occur, notwithstanding 

 some false records by visitors to Ireland. The small delicate white 

 lipped H. neinoralis so plentiful tn some north-western dunes has 

 been mistaken for H. hortensis. 



