DEPOSITS AND ELEVATION. 25 



With regard to these shells, it is to be observed that 

 they occur either massed in heaps or layers (generally of 

 one or two kinds together), or more sparsely distributed 

 throughout the bed. They are all of species eaten by 

 birds or man. All the specimens are full-grown, or at 

 least of edible size. They are nearly in every instance 

 whole, the exceptions being the Mytilus, a shell peculiarly 

 liable to disintegration, and the Littorina, which often 

 occurs with a broken outer lip, as if the shell had needed 

 this fracture to allow of the extraction of the animal. 

 There are neither any other species, nor any young spe- 

 cimens of those that do occur. 



Lastly, the clayey detritus cannot have been a habitat 

 for any one of these species, even if it were of marine 

 deposit, which it is not ; nor would it be possible for the 

 shells to mass in the patches in which they sometimes 

 occur, at the foot of sea- washed cliffs, or in fact, I venture 

 to say, under any conditions of original natural deposit; 

 or if they did, to remain so, on an exposed beach or 

 a sea-bottom, during a protracted period of elevation 

 through the tide. 



The fact of elevation is undoubted; but these shells 

 are no evidence of it. 



It is not necessary to give separate lists of the particular 

 lots of these species which occur at different heights. 

 They or some of them have been found in the eastern, 

 northern, western, and southern slopes, and especially 

 in the cuttings of the "old road^^ up the hill, and the 

 Hen Dafarn road towards the east. On these lines 

 they have been noted at 120 feet, at 140 feet, at 180 

 feet, at 200 feet, at 300 feet, and at 315 feet above 

 the sea. 



On the old-road sections, especially in the upper levels, 

 the shells are not unfrequently accompanied by teeth and 

 fragments of bones of Mammalia and bits of charcoal. 



