122 PEor. T. m'kenny hughes 



to be recorded is the ScandiD avian coast, on the anthority of 0. F. 

 Miiller. The variety elliptica (" shell invariably smaller than the 

 typical form, broader in proportion to its length, in consequence of 

 the sides being more produced, and of a thinner texture") has 

 essentially a northern range, from Iceland to Kulla in the south of 

 Sweden *. 



In the table given above (p. 120) I have indicated which of the shells 

 found in the drift outside Cae Gwyn Cave occur also in the marine 

 drift at St. Asaph and Colwyn ; which are common to the glacial 

 beds of Bridlington collectively ; and which are found on our coasts 

 at the present day. 



These shells prove conclusively that the high-level drift at Cae 

 Gwj^n is not " a true undisturbed glacial deposit," but that it 

 belongs to the St. Asaph Drift, which "is mainly remanie " t« 



The deposit itself consists of fine sand, clay, and gravel, with 

 boulders of various size and origin scattered through it. It is not 

 such as would occur along a shore lashed by the wind waves. The 

 whole of the rocky ledges and most of the fissures and caves would 

 have been swept clean by such a sea. But it might easily have 

 resulted from the working-down of debris from cliif's of older drift 

 after the land had been submerged far enough to sink these crags 

 below the action of the waves. When it was rising from the sea, 

 in the emergence which followed, there was such a mass of drift 

 hanging on the hill-sides that it has not yet all been washed away, 

 and the remaining patches protect the material first thrown down. 

 But that a cave or terraced crag not so covered can ever have been 

 at sea-level without being swept clean is difficult to believe. The 

 preservation of cave-deposits under land-ice drift from Snowdon and 

 Arenig is credible ; but an examination of the deposits shows that no 

 part of those exposed can be referred to the land-ice drift ; more- 

 over, the discovery of the shells in the drift outside this cave con- 

 clusively proves that it was not the land-ice drift, but a marine de- 

 posit derived from it, some having worked down the steep slope into 

 deep water, while part was subaerialLy derived from it at a much 

 later time. 



The mixture of north-country boulders and flint in the same 

 deposit with those from the west is very marked and difficult of 

 explanation ; but this locality cannot have been far from the line 

 along which the terminal deposits of the northern and western ice 

 met, as a little way to the west we find the glacial drift exclusively 

 of western origin, and a short distance to the north-east we find the 

 drift wholly made up of material from the north and east. If that 

 be so, we may expect that some glaciated stones of northern origin 

 may have got washed into the marine deposits of the lower part of 

 the Yale of Clwyd without obliterating the striae ; but, for some 

 reason or another, they have not yet been found in the drift near 

 St. Asaph ; possibly they may occur on the higher ground to the east. 

 The deposit inside the Cae Gwyn Cave cannot be synchronous 



* Gwj^n Jeffrey's ' British Conchology,' vol, ii. pp. 417, 418, 

 t Hicks, Quart. Journ. Geol. Soc. vol. xHii. 1837, p. 117. 



