290 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



S.S.W. 60°, and in another S.S.E. 60°. A greenstone dyke, run- 

 ning north and south, cuts the beds without disturbing them. 



Besides some of the fossils of Glyn Diffwys contained in the list 

 given by Professor Sedgwick, the author found Orthis radians (Si\. 

 Syst. pi. 22. fig. 1) and Favosites fibrosa. 



The rotten schists of Glyn Diffwys rest upon hard blue slaty Bala 

 grits, which contain some Lower Silurian fossils. These are con- 

 tinuous westward from near the sixty-first milestone for nearly 

 twelve miles, across the dreary moors of Cernioge and Pentre Voelas. 



In the eastern portion of the district the beds undulate, as will 

 appear from the following table. 



Distance from 



Dip of the 



Holyhead. 



Bala Grits. 



m 





60 



E.N.E. 20 



58i 



N.W. 15 



m 



s.E. 30 



58i 



! 



N.W. 20 



In consequence of these undulations they are several times re- 

 peated. Their prevailing strike is north-east. They do not extend 

 far to the north of the road, but are covered up, along a line pass- 

 ing nearly east and west, by unconformable Wenlock rocks. The 

 grits found to the east of Cerig-y-druidion split readily along the 

 bedding, and are fossiliferous. The most abundant of the fossils 

 are two unnamed species of Orthis, which occur also in the Bala 

 limestone. 



Near Yspytty Evan*, a village on the river Conway, the Bala and 

 Hirnant limestones may both be seen, with their attendant upper 

 slate and schists. These beds lie in a sort of trough. About a 

 mile and three-quarters south of the village, on the left bank of the 

 Conwaj'^ river, the Bala grits are seen, containing an abundance of 

 Leptcena sericea. Here they dip N.N.W. 20°. To the north of 

 this point about a quarter of a mile, the Bala limestone appears in 

 a position parallel to that of the grits. Further north, about a 

 quarter of a mile south of the village, the Hirnant limestone, ac- 

 companied with fossiliferous schist, crosses the road, its beds dipping 

 north 25°, its cleavage north 60°. North of the village the fossilife- 

 rous schist and upper slate abut unconformably against the Bala (?) 

 grits. 



Carnarvonshire. 



Every traveller on the road to Holyhead, after leaving the forty- 

 seventh milestone, must be struck with the sudden change of 

 scenery. From the dreary moors of Cernioge and Pentre Voelas 

 he passes at once to the picturesque beauty of Bettws-y-Coed, 

 while before him are ranged ruga:ed hills of slate alternating with 

 hornstone and greenstone. This change takes place at a vast 

 dike of greenstone, which forms a high crag on each side of the 

 road. Its course is from S.S.W. to N.N.E. In the latter direction 



* In Mr. Greenough's map the occurrence of limestone is marked at Yspyttj 

 Evan, and also at Penmachno, a place which the author did not visit. 



