1^98.] 77 



LAND-SHEI.I. " POCKETS " ON SAND-DUNES. 



BY R. WEIvCH. 

 (Read before Belfast Naturalists' Field Club, January i8th, 1898.) 



Among the sand-hills in the North and North-west of Ireland 

 one may often find large quantities of land-shells collected in 

 little hollows or " pockets," especially at the east end of 

 Whitepark Bay, North Antrim, and on the Portstewart dunes 

 near the River Bann. Some of the shells in the case of the 

 smaller species may be alive, but the great majority will be 

 found dead, and worn thin and smooth by drifting about 

 with the sand, any sculpturing on the shells being removed. 

 Of these dead shells, however, some are often quite fresh and 

 uninjured, and possibly a number may be rare and difficult to 

 find alive. I have given the ''pockets" a good deal of 

 attention on various visits, wondering at the large number of 

 the rarer species which it was possible to collect in this waj^ 

 even in a single " pocket " a few feet square, and species too, 

 which do not take kindly to such dry exposed places, but 

 prefer the moisture and shelter of thick vegetation or damp 

 mossy slopes. Visits paid during windy weather soon taught 

 me that the shells often travelled a long way before being 

 collected by the swirling action of the wind round the dunes 

 into some sheltered hollow, or little plateau covered with Bent 

 {Psavivia arenarid)y which stopped their progress while 

 allowing most of the sand to pass through. Where the Bent 

 was the collector, the shells were usually mixed with a mass 

 of dead leaves, grass, beetles, &c., and here I usually found 

 some of the shells alive. 



At Whitepark they came mainly from the broad steep grassy 

 slopes, running up from the dunes to the bottom of the cliffs 

 which bound the bay. These mossy swards have a great 

 variety of food-plants, and lying under the Chalk cliffs, on the 

 I^ias and Chalk talus below, damp for the greater part of the 

 year, provide the proper conditions for an abundant shell-fauna. 

 Few shells come out in dry weather, and especially in the day 

 time, when they hide or burrow in moss or at roots of grass, &c.; 

 at sundown, however, or in wet weather, swarms of them 

 may be seen feeding all over the sward, and on the Thistles, 

 Bent, &c.) on the dunes below; It is this sudden appearance 

 of great numbers of some species, Helix virgata and H. acuta 



