338 



POCKETS OF LAND-SHELLS, BANNMOUTH DUNES, 

 PORTSTEWART. 



By R. welch. 



(Read before the Society, May 13, 1903). 



A SMALL area of County Derry will be noticed on a map to the east 

 of the River Bann ; this is known as the north-east Liberties of 

 Coleraine. Jutting out due west of this and north of the mouth of 

 the river, may be seen a little point ; this is covered with high sand- 

 dunes, long famous for the remains of pre-historic settlements and the 

 many stone implements found there. At the eastern end of the point 

 the dunes are more permanent than further west ; there are large 

 areas of mossy sward, and close to the river marshy areas with a most 

 luxuriant vegetation, ideal habitats for many of our smaller and rarer 

 land-shells. The sward here is one of the main stations in Ireland 

 for Helix interseda {-^=caperata\ and it was while collecting this 

 species, about ten years ago, that I found in the dune hollows close 

 to this moist area a number of fine shell "pockets."^ These nature- 

 winnowed little collections of small shells should never be ignored for 

 they often contain (and this may not show till the mass is sifted) large 

 quantities of Vertigoes, the smaller Hyalinse and Helices, and in the 

 late summer or autumn a proportion of these may be alive. Vertigo 

 afigustiot; Helix pulchella, H. costaia, and sometimes H. aculeata 

 abound in these pockets with an occasional Acme, the species and 

 their relative abundance depending on the nature of the feeding- 

 ground fringing the sand-hills. For instance. Vertigo pusilla and its 

 var. albi?ia (the latter first found by Mr. Standen in a Portsalon 

 "pocket") are more plentiful at Portstewart than anywhere else in 

 Ireland, except perhaps Narin dunes, West Donegal.- 



Finding myself on these Bannmouth sand-hills a few days ago, I 

 searched in the usual places, the dune-hollows, or rather some little 

 plateaus close to a hollow, for some pockets, in vain ; I was not sur- 

 prised at this, as I had never found these in the winter or early spring. 

 Yet it was evident there must be accumulations of shells somewhere, 

 as the higher dunes from their ragged summits, with marram grass 

 root-stocks, etc., all felted together, had evidently undergone unusual 

 denudation this winter, probably during the late cyclone, setting free 

 many old shell-pockets. Leaving the low ground and climbing among 

 the high loose dunes, Mr. R. LI. Praeger and I soon came on a ridge 

 which was growing on the eastern side from rapid seolian erosion on 

 the west. Masses of Psamma roots had collected here and there 



1 Irish Naturalist, vol. 7, March, 1898, pp. 78 and 81 



2 Farran, oJ>. cit., vol. 8, August, 1899, p. 1S4. 



