WELCH : POCKETS OF LAND-SHELLS, BANNMOUTH DUNES. 339 



among growing plants, and arrested by these in their downward course 

 on the lee side of the dune were about twenty fine little pockets of 

 shells. These were collected under conditions which kept them to- 

 gether, on the side of a steep dune, an impossibility in dry summer 

 weather, when the pockets caused by wind-eddies are formed. As 

 usual, no examples of Vertigo were to be seen, but I knew they were 

 there, so as the material was too damp to sift on the spot, I brought 

 about three pints away in a bag, and it is the shells sifted out of this 

 I send for the acceptance of the members, to give them an idea of 

 the richness of our Irish dune fauna, so far as moUusca are concerned. 

 It must not be supposed that all these dead shells are dull and opaque, 

 many fine fresh specimens occur. I know conchologists who have 

 never yet been fortunate enough to find good pockets, but they are 

 not always present. Very wet weather and very windy dry weather are 

 unfavourable to their accumulation, and the conditions also vary with 

 the character of the dunes. It was near this that Mr. Lionel E. 

 Adams collected the first Irish specimen of Vertigo alpestris ; this I 

 have not so far been able to find in these particular pockets, though 

 it lives in dunes a few miles to the eastward. Perhaps some of those 

 who examine this material may be more fortunate. Very pale coloured 

 V. pygmaa occur which at first glance might be mistaken for it. 



After dry windy weather any ponds in the dune-hollows should be 

 carefully examined, as these sometimes have nice floatings of the 

 smaller species collected as a fringe along the lee-side, the sand sink- 

 ing. Some of what I send were collected in this way, and Mr. Prae- 

 ger's fine collection of Vertigines from Bundoran^ was found naturally 

 floating along the dune margin of the River Erne. Here, three years 

 ago, I saw an incoming tide quietly floating up large quantities of 

 small shells, including many specimens of Vertigo that had been 

 blown off the sand-hills on the strand during very windy weather. I 

 found twenty-four species in all in the Bannmouth pockets, and 

 among these the following : — Hyalinia pura, Helix aculeata, H. pyg- 

 tn(2a, the white-shelled forms of Pupa mtiscorum, and F. cylindracea 

 (not merely bleached specimens). Vertigo ajigustior, extremely plenti- 

 ful, V. pygnicea, V. substriata, V. antivertigo, and both type and var, 

 albiua of V. pusilla in moderate quantities. 



It is curious to find fair numbers of Claiisilia bidentata in this way, 

 and always thin and fragile, as they are also at Achill (where it seems 

 to be extinct now) and Rosapenna dunes. Can these be derived from 

 old pockets collected when the dunes were covered with natural 

 thickets, or when less broken into than they are now ? Natural habi- 

 tats for Clausilia. are a good distance away from some of these dunes, 

 where they are found in numbers dead. 



I Of. cii; vol. I, 1892, p. 171. 



