24 MR. R. D. DARBISHIRE ON GREAT-ORME's-HEAD 



and the great inclination of the slopes preclude the 

 possibility of ascribing these beds to the action of the 

 sea on the sides of the rising Head. 



On the other hand the predominance of angular frag- 

 ments, their promiscuous aggregation, and the slight bed- 

 ding along the line of surface mark the whole as subaerial 

 talus. The formation is modified in local character by 

 the greater or less gradient of the slope, and latterly by 

 the decrease of that inclination and the increasing luxuri- 

 ance of vegetable growth of grass and bushes. 



The clayey material is probably principally derived 

 from the decomposition of the limestone rock"^, modified 

 and perhaps augmented by vegetable growth, secretion, 

 and decay ; but the occasional occurrence of rounded 

 pebbles of other minerals probably indicates a redistri- 

 bution, under the like influences, of patches, at least, of 

 boulder-clay. 



It is in one or other, and especially in the latter, of 

 these two beds that observers have frequently noticed 

 the occurrence of shells of the species Mytilus edulis, 

 Cardium edule, Ostrea edulis, Patella vulgata, Littorina 

 littorea, Purpura lapillus, and Buccinum undatum. 



Mr. Binney mentions having tracked these shells up 

 the hill towards the bed of shingle at a height of 400 feet, 

 and deduced proof of the elevation of the Head at least 

 that height during a very modern epoch. 



In the same year Mr. Sidebotham (from whom I re- 

 ceived my first specimens) exhibited extensive collections 

 of these remains ; and he and others have since extended 

 his observations. I believe Mr. Dancer was the first of 

 our members to note the occurrence of these fossils. 



In 1867 Mr. Bonney described (Geol. Mag. iv. 289) a 

 deposit of shells, near Gwydfyd farm, from the uppermost 

 bed. 



* I am told that this limestone is noticeably argillaceous in character. 



