Vol. 54.] LIMESTONE OP THE COUNTKY AROTJND LLANDUDNO. 397 



The southern range of hills extends from Bod-y-Sgallen for 

 3 miles in a north-easterly direction, but does not appear to have 

 any definite name. It presents exactly the same geological structure 

 as that already described, the subdivisions consisting of the Lovrer 

 Brown Limestone with the Middle White Limestone resting upon it. 

 The only difference is that the dip is reversed, so that while the 

 limestone in the northern range dips south-east, that of the southern 

 range dips north-west, and there is a synclinal valley about a mile 

 in width between them. Along the south-east of the valley the 

 Middle White Limestone everywhere dips about 20° or 25° to the 

 north-west. Over a considerable area the surface descends with 

 the dip to the valley until covered by the cultivated land, and there 

 is no indication of the Upper Grey Limestone in any part of the 

 valley. 



West of Pabo there are three large quarries, the one nearest 

 that place being excavated in the side of a conical hill, and, 

 except in colour, it presents a strikiug resemblance to several of the 

 breached volcanoes of Auvergne. The limestone in this quarry is 

 of a massive character, 90 feet thick, and traversed by joints which 

 give it the appearance of being vertical. At the base of the quarry 

 the limestone assumes a darker colour, is thin-bedded, and represents 

 the Lower Brown Limestone, 30 feet thick, in which I saw several 

 specimens of Productus comoides, but none in the overlying sub- 

 division. 



The Lower Brown Limestone has a continuous outcrop along the 

 south-east of the range, and the base occurs parallel with the road 

 at Llangwstenin Hall. Half a mile farther north there is a quarry 

 where a black shale, having much the appearance of lignite, occurs 

 a few feet above the level of the road. It is from 3 to 6 inches 

 thick, but only extends for 10 yards, with a dip of 18° N.N.E., 

 and must be near the base of the subdivision. There are beds of 

 impure limestone above the black shale, and beds of dolomite 14 feet 

 thick below it. The limestone rests unconformably upon the Wen- 

 lock Shale, and there is an alluvial valley along the east of the 

 road. 



Bryn Dinarth, or Bryn Euryn (named after the ancient British 

 entrenchment at the top), is the conspicuous hill east of the valley, 

 which separates it from the portion of the southern range already 

 described, and is only a mile from Colwyn Bay. It is formed of the 

 Middle White Limestone resting upon the Lower Brown Limestone, 

 as in the hills on the west. On the north, the Middle White Lime- 

 stone descends from the summit of the hill, which is 427 feet high, 

 to the north of Llandrilloyn Bhos Church, and forms all the upper 

 part of the hill with the exception of the semicircular ridge of 

 Lower Brown Limestone, which crops out to the south. The Middle 

 White Limestone exhibits its usual massive character : it is quarried 

 at the northern end of the hill, where it dips 16° north-west, and is 

 of a light colour. Another quarry on the east, just above the 200- 

 foot contour-line, shows the white limestone 20 feet thick, resting 

 on the dark grey beds of the inferior subdivision 40 feet in thickness, 

 with a dip of 17° north-west. 



