260 [Nov. 29, 



Section IV. a. 



Ckaig-y-glyn, three miles and a half to the west of the line of Section IV. at 

 the point marked 6. 



Horizontal base 2^ miles. 



S. I.laniarmon N. u 



Craig >• Jlvnvdd Alvnjdd j 



CefnjnxTfa. Ulyn. Mawr. iUawr. hj 



Tanat, a sei'ies of slates (9), not differing in their mincralogical 

 character from the slates of the higher Berwyns ; and in these, at 

 a great depth as measnred from the Caradoc sandstone, are found 

 calcareous bands, full of fossils, among which are Asaphus Buchii, 

 &c. The Craig-y-Glyn limestone {vide Section IV. a.), which 

 appears to the north of Llanrhaiadr, at the distance of nearly 

 four miles to the west of the line of Section IV., the author regards 

 as belonging to these bauds. 



[The Craig-j'-Glyn limestone has most of the species of tlie Rliiwlas lime- 

 stone ; but the abundance of Asaphus Biic/iii, of OriJiis co7iipressa, of a new- 

 species of Orthis, and of Encrinital stems, give it a peculiar character.] 



4. Still lower in the series are similar slates ; but they are 

 without fossils, and, after several breaks or iindulations, the beds, 

 about two miles further to the north, are found to have acquired a 

 steady northern dip. 



5. South of Pont Meibion, on the Ceiriog, fossils again appear, 

 conforming to the types of the lower portion of the protozoic 

 group. 



[The lower part of the series near Pont IMeibion may be only a repetition of 

 the Craig-y-Glyn series, with a reversed dip. But the higher part of the series, 

 ■which ranges over the crest of the Berwyns by Bwlch Llandrillo, contains only 

 Bellerophons, particularly a new species, B. vodosus, found also at Soadley, in 

 Shropshire, by Mr. Salter. At Bwlch Llandrillo, a new Orthis, O. camlriaisis, 

 which is also found in the Bala series, is abundant ; and to this may be added 

 many other species of Orthis, which that scries contains. ] 



6. Then follows, in the ascending section, a great series of beds 

 full of fossils, and these beds alternate with bauds of cotempo- 

 raneous porphpy, schaalstein, &e. 



7. Lastly, there is a well-detined thick group, whose width, 

 measured transversely to the strike, is about a mile. It is com- 

 posed of calcareous slates, and contains two bands of limestone, 

 "both of which have been worked for lime. It passes upwards into 

 pale-coloured earthy slates (d), and these seem to pass, without a 

 break, into the overlying Denbigh flagstone (e), which just appears 

 on the southern bank of the Ceiriog, and extends northward from 

 that river towards the vale of the Dee. The fossils both of para- 

 gi'aphs 5 and 6, are entered in the list of the Ceiriog fossils. 



