196 Mr. Bowman on Silurian Rocks ivest of Abergele. 



impure coal about a foot thick, and a thinner layer of bituminous shale with car- 

 bonized impressions of fine branches of Lepidodendron (?) and a leaf-like Poacites. I 

 found also a small head of a species of Encrinite. Immediately under the limestone, 

 at the foot of these precipices, is a thin seam of rounded pebbles of a greenish, 

 slightly micaceous sandstone, containing a few bivalves and joints of Encrinites im- 

 bedded in a light loamy earth, and resting upon a thin bed of the same greenish 

 sandstone (see/, woodcut). This pebble bed was in situ, and I afterwards saw it 

 in situ also, and under the limestone, in several places on the north side of the cal- 

 careous formation ascending from the shore of LlandrilloBay toColwyn on the Holy- 

 head road, but in these places the pebbles were often six, eight, and even twelve 

 inches in diameter. Proceeding south or a little west of south from Craig y Forwyn, 

 in the line of the section, I came upon a thick stratum of red marl (e, woodcut), in 

 which are imbedded very numerous angular and water-worn pebbles, both of red and 

 blue sandstone, the red most abundant, and of a liver-colour, compact, and mica- 

 ceous, and imbedding many species of bivalves, apparently like those in the Lud- 

 low rock. This marl forms the soil to the head of, and a considerable way down, 

 Ffernant dingle, through which a little rill runs from north to south, and has hol- 

 lowed out the banks so as to show a very good section. These pebbles are likewise 

 found in the neighbouring fields, often attaining the dimensions of large boulders; 

 also on the top of the limestone precipices, and beyond them on the beach below. 

 In following the rill down Ffernant dingle, this bed varies in its characters into a 

 compact marl or soft rock, and to a marly conglomerate, and is sometimes vari- 

 egated with greenish and yellowish specks, but it has a pretty uniform dip to the 

 north, at a considerable angle. From the extent of surface it covers, it is probably 

 of considerable thickness. Underneath, or perhaps what is more properly its 

 lower portion, is a compact arenaceous conglomerate {d, woodcut), forming a hard 

 rock, and containing pebbles of liver-coloured and green, micaceous, shelly sand- 

 stone, more or less rounded ; in some places mostly of small size, but in others much 

 larger and coarser. In an adjoining wall I saw several boulders of this conglomerate 

 more compact, and some quartzose and even jaspery, strongly resembling the rock 

 near the Menai bridge and also one near Caernarvon. Still following the rill, 

 this conglomerate is found lower down, resting on thin beds of compact reddish 

 limestone (c, woodcut), containing few organic remains, and some irregularly-shaped 

 fiattened nodules. Pieces of this limestone are imbedded in the arenaceous conglo- 

 merate, and in one of them I observed a broken Euomphalus. The limestone is 

 often so arenaceous as to become a calcareous sandstone, and sometimes it is as 

 smooth and compact as the rock called Flummery-stone, which I have seen at 

 Llanymynech, and at Coed Marchan in the Vale of Clwyd. 



Near the lower end of the dingle, and just above a level on the right or west 



