1909. Wklch. — Land-shell Rain-wash in Co. Donegal. 1 13 



LAND-SHELL RAIN-WASH AT HORN HEAD 



CO. DONEGAL- 



BY R. WELCH, M.R.I.A. 

 (Read before the Belfast Naturalists' Field Club, 3rd March, 1909) 



In recent 3^ears the little pockets of land-shells, that are 

 collected b}^ the wind in hollows of the sand-hills, have received 

 a good deal of attention from conchologists, who find such 

 collections useful in survey work. When sieved free of sand, 

 they often provide a good index to the molluscan fauna of a 

 dune-area and the immediate district. This is especially true 

 of the very small species such as Vertigo, which are often most 

 difficult to find otherwise. Though these pockets consist 

 largely of shells drifted b\' the wind from similar deposits in 

 old dunes now undergoing erosion, they often contain living 

 shells and others not long dead as well.^ For that reason, 

 while a party consisting of F. Balfour Browne, G. W. Chaster, 

 Ed. Collier, J. N. Milne, C. E. Wright, A. W. Stelfox, and my- 

 self were, last September (1908), visiting north-west Donegal, 

 we kept a keen look-out for such " pockets '' or shell deposits 

 generally, as A. W. Stelfox had found many on a previous 

 visit with Dr. Chaster, in 1905. Heavy rain before our arrival 

 had spoiled most of the pockets, but while walking up a long 

 dune valley at Tramore, Horn Head, some of the party in 

 advance called my attention to some narrow dark bands from 

 one to two inches thick in a remnant of an old dune that was 

 rapidly undergoing wind-erosion. On examination we found 

 the dark bands consisted of immense masses of small land- 

 shells loosely cemented together by fine mud, but quite unlike 

 any dune deposit we had ever seen or heard of. Shells some- 

 times collect in shallow pools in dune hollows, but the matrix, 

 when the pool dries up or is filled up with sand, is usually 

 earth}' sand, and only a few of the larger species that live on 

 sand-hills are present. No one thought of a " rain-wash " in 

 the middle of a great sand-hill area, yet it was clearh^ a deposit 

 formed by water in some wa}'. On climbing over a growing 

 dune close at hand, that was encroaching on a bare hillside 

 area, Mr. Wright found a ke}' to the mystery. Here, in a little 

 hollow between the dune and hillside, was an exactly similar 



^ See R. Staudeu, I.N', vi., p. 2, 1897 ; R. Welch, nl vii., p. 77 7898. 



