202 [Proc. B.N.F.C., 



deposits, and are protected till the dunes undergo erosion, from 

 any cause. In the changes which are constantly taking place in 

 most seolian sand hills this may be the case in a few months or 

 years, or may not occur for a very long period. Where the 

 deposits are collected in sand which is mainly silicious, the shells 

 are liable to solution by percolating waters, which dissolve out the 

 calcareous substance. For this reason such deposits are rare — 

 usually absent — in our east coast sand hills, but they are often 

 very abundant in the calcareous sand dunes of the west coast of 

 Ireland, the sand of which is mainly finely comminuted shells and 

 sea-urchins, with the tests of foraminifera, &c, present sometimes 

 in large quantities. At Horn Head land shells occur in the dunes 

 in myriads, and, where the dunes have been formed along a 

 hillside, having a surface of stiff clay, sudden heavy rainfalls 

 rushing down the slope have undercut the dunes, floating out 

 shells of all sizes and carrying them down to hollows in the sand. 

 Here the water filters away, leaving the shells in a layer of mud 

 to be covered up by dry blown sand during the next dry windy 

 period, possibly only a few hours afterwards. A succession of 

 these rainwashes separated only by a few inches of sand showed 

 clearly in one section. Mr. Welch described the washing out of 

 the mud, when over twenty species of shells were determined in 

 the mass, the most interesting fact being the presence of very large 

 numbers of the genus Vertigo, including the rare V. pusilla. 

 Specimens were shown of the material collected by the lecturer at 

 Horn Head. 



An animated discussion followed the lecture, in which the 

 following took part — The Chairman, Messrs. F. Balfour- Browne, 

 M.A., A. W. Stelfox, T. H. Dewhurst, A.R.C.Sc, N. H. 

 Foster, M.B.O.U., H. L. Orr, W. J. C. Tomlinson, J. N. Milne, 

 George Donaldson, and C. M. Cunningham, L.D.S. Mr. Welch 

 replied to numerous questions. 



