114 The Irish Naturalist. Hay, 



deposit in the course of formation. Heav}- rain, sweeping 

 down the hillside against the encroaching dunes on two sides, 

 had washed masses of shells, mostly from old deposits, into 

 the hollow, where they had collected as a natural floating, to 

 be deposited on the surface of a la3'er of jSne mud as the water 

 filtered awa}^ through the sand. The day was dry and windy, 

 and sand coming up over the dune from the west was already 

 covering up the shells and would soon press them into the 

 soft mud, and give a thin dark band in the sand, full of shells, 

 like those in the old dune. This was clearly the way the 

 older deposits had formed, and if we had dug down under the 

 new one we would likely have found several others separated 

 by sand. The species too were the same, and with few 

 exceptions were the shells any fresher than in the older 

 deposits. 



Though rain-wash shell-deposits are not uncommon on hill- 

 sides and in the rifts of rocks, limestone especially, I have 

 never seen nor heard of one in a sand-dune before. The 

 others, too, contain only a small proportion of shells compared 

 to the general mass, while the reverse was the case in these 

 Tramore deposits. Modern examples of the way in which 

 local masses of shells, or other debris of animal or vegetable 

 origin, ma}" form deposits, are of interest. They point the 

 way in which somewhat similar fossil masses present in the 

 older rocks may have been formed. The mass of shells was 

 taken to our hotel and washed free from the muddy matrix in 

 a sieve of fine miller's gauze. It was then seen that the 

 general condition of the shells was as good as if they had been 

 sieved out of modern shell-pockets. Even the tin}- Vertigo 

 and Carychium were perfect, and many of the Cochlicopas were 

 as glossy and translucent as if only recentl}' dead. The fine 

 matrix had, of course, a good deal to do with this ; but in 

 these western sand-hills of calcareous sand, shells are much 

 more perfectly preserved than in the silicious sandhills of the 

 east coast of Ireland. Rain percolating through the latter 

 soon dissolves out shells and any other calcareous matter 

 present, but where the dune-sand is itself calcareous, the water 

 quickh' gets saturated and unable to do harm. 



The sand is largely calcareous at Horn Head, containing as 

 it does finely comminuted marine and land shells, Foramini- 

 fera. Urchin tests and spines, &c., which form so much of the 



