MONIAN SYSTEM OF ROCKS. 523 



Traced further to the east, this quartz dies out with the crest ; but 

 on the south side of the line there are several smaller quartz-knobs 

 at various horizons, and on the north beds of finer conglomerate are 

 intermingled with the ashy slates, which have a strong resemblance 

 to those of Berth Wen, and these continue to the coast. The whole 

 of the ashes and conglomerates of this group are highly cleaved, with 

 a cleavage-strike parallel to their bedding. Neither conglomerate 

 nor quartz-knob is to be found in the coast-section of Bull Bay; and, 

 in spite of a careful search, on two or three occasions, between the 

 slates of Amlwch and the ashy rocks of Trwyn Melyn, I have not 

 been able to fix on any line of break at all. 



In considering the bearing of these facts, it must be admitted 

 that if no fossils had been found I should unhesitatingly have 

 considered all the rocks seen east of Forth Llanlliana, except the 

 undoubted Ordovician slice at Forth Fridd, as belonging to the 

 Fre-Cambrian series. The occurrence of conglomerates naturally 

 suggests a new series ; but when the rocks above and below the 

 conglomerates are so similar, and every attempt to find a line of 

 separation on the coast, where all is clear, has failed, one is fain to 

 admit a conformable succession through the whole ; and this view I 

 still hold to be most probable, and am quite ready, if possible, to 

 receive the fossils as characteristic of the system. Against the 

 belief that these are true Bala fossils we have the fact that they are 

 not like any other fossils in the island, though Bala beds are 

 supposed to be found elsewhere ; and the rocks that contain them 

 are not like the other fossiliferous beds, which are found so close at 

 hand. Even if they were Bala fossils, they could not possibly carry 

 all the rocks of the northern district with them, since these are so 

 clearly identical with those in the eastern district which are 

 overlain by Cambrian, and they are in this very neighbourhood 

 overlain by typical Ordovician. We should therefore have to find a 

 fault or unconformity somewhere ; none has yet been found, though 

 it might be obscured by cleavage, and conglomerates might suggest 

 it ; but even thus it would be difficult to account for the neigh- 

 bouring Ordovician conglomerate at Ogo-gyfwr, &c. 



As regards the fossils themselves, they are referred to OrtJiis 

 Bailyana by Frof. Hughes, and this fossil is said by Davidson to be 

 associated in Wexford with Leptcena sericea and other undoubted 

 Ordovician fossils. By the kindness of Frof. Hughes I have been 

 able to examine his fossils, and one of them is undoubtedly 0. 

 Bailyana, while others do not seem identifiable with any described 

 species. It will therefore become of importance to examine the 

 true stratigraphical position and age of the rocks in Wexford in 

 which this fossil occurs. 



Summary of the Northern District. 



The district is isolated by a curved fault, which is broken near 

 Farys Mountain, and has a general hade to the north, along which 

 the older groups have been pushed up over the black Ordovician 



