20 NOTES ON THE GEOLOGY OF 
the upper bed is pitted with holes like those made by pholas 
weathered out. Here it is impossible there can have been any 
lithodomous molluscs. The opening out of the joints on a small 
scale so as to produce fine lines like glacial striz is well seen 
in the quarries N. of Tyddyn Uchaf, N. of Denbigh, and the 
larger gaping fissures, running straight on for many yards, due 
to the weathering along master-joints, may be well seen over the 
top of the same hill. 
Nowhere have I ever seen such a curious imitation of bedding 
produced by infiltration bands as in the sandy flaggy beds of the 
Craig Quarry, near Denbigh. The rock is generally of a buff 
or grey colour, and the bands are of a darker tint approaching 
black. They are seen following the joints all round near the 
margin of the slab, but rounded offas they get further in (fig. 10.) 
A fragment broken off the side of the slab would certainly be 
taken for a laminated rock, in which the bands of colour 
indicated difference in lithological character, due to original 
deposition. Similar phenomena, but not so well marked, are 
not uncommonly seen in the Silurian flags. In one locality in 
Yorkshire all the débris on the hill side consists of flat stones, 
ringed and banded in purple and red. These rocks, which are 
known as the ‘‘Moughton Whetstones,” are of exactly the age of 
our Denbigh Flags and Grits, which frequently exhibit the same 
markings, where they occur near the base of the Devonian, as 
seen E. of St. Asaph or W. of Denbigh in many places. 
Fic. nro. 
Slab of Mountain Limestone, showing the bands produced by 
infiltration from joints, Denbigh. (Scale, 2 feet to 1 inch.) 
Tue NEw RED SANDSTONE. 
It will be seen from the above observations on the Carboni- 
ferous Rocks that the area of the New Red will have to be 
reduced considerably when we have taken out all the stained 
Carboniferous, and, as these were the only variable beds, what 
remains requires no long description, for it agrees with the great 
masses of New Red in other districts, in consisting of an 
enormous deposit of red sand of very uniform texture all through, 
and quite unfossiliferous. Aveline (Expl. Hor. Sect., Geol. 
Survey, Sh. 43.) says—‘‘ The New Red Sandstone in the Vale of 
Clwyd is believed to be that subdivision known as the Lower 
Red and Mottled Sandstones of the Bunter Series. It lies quite 
unconformably to the rocks beneath which have been disturbed 
and denuded before it was deposited, and thus, as may be seen 
by referring to the map, it rests indifferently on the Limestone, 
the Old Red Sandstone, or the Silurian Strataa * * * The 
structure and composition of these sandstones are much the 
same throughout the Vale; and in sinking a well at Ruthin, to 
the depth of 400 feet, the same kind of rock was found from top 
