60 *m MR SMITH ON THE CHANGES 



been filled with blue clay ; but I have observed the same 

 thing in shells which certainly belonged to the stratified de- 

 posit, and it is easily accounted for. The action of the sea 

 upon such a bottom would naturally stir up the clay so as 

 to fill dead shells. Those found in this locality do not bear 

 marks of violent transportation, and the distance from the 

 sea is so great that it is difficult to suppose that such fragile 

 shells as the Mytilus edulis and Tellina approxima could 

 have been borne along uninjured by diluvial action. I am, 

 therefore, inclined to consider, that the shells found at 

 Airdrie belong to the alluvial beds, and have been con- 

 firmed in this opinion by having had some specimens of 

 the Tellina approxima, a species which has only been found 

 in this deposit, sent to me from the same locality. 



Mr Prestwich* also found, at the height of 350 feet, in 

 beds of sand, gravel, and clay, at Gamrie, near Banff, the 

 following recent shells : Astarte Scotica, Tellina tennis, 

 Buccinnm undatum, Natica glancina, Fusns turricola, 

 Dentalium dentalis. They were extremely friable, but per- 

 fectly uninjured. 



The promontory of Brayhead, in the county of Wicklow, 

 is formed by a cliff of alluvial strata of coarse gravel and 

 sand, containing sea shells ; it is at least two hundred feet 

 high, and the hill of which it is a part, and which is evi- 

 dently composed of the same beds, is perhaps a hundred 

 feet higher. Here, therefore, this deposit reaches to the 

 height of three hundred feet. At Howth, on the north 

 side of Dublin Bay, are similar cliffs, at the height of 

 about a hundred feet, also containing shells and other ma- 

 rine exuviae. 



In the Isle of Sheppey,f recent shells have been found in 



* Proceedings Geol. Soc. May 3. 1837- t lb. vol i. p. 410. 



