242 MK. C. A. MATLET ON THE [May IQOO. 



Llandeilo), each in their proper order, but with many of their 

 component beds cut out and others repeated. The Green Series is 

 followed by Llanbadrig beds of limestone (some of which has been 

 burnt for lime), quartzite and slate, and crush-conglomerates of 

 slate and grit. These beds are faulted, broken, and repeated ; the 

 upper beds of this Series and the lower beds of the Llandeilo are 

 wanting, but the Upper Llandeilo Beds are present, as already 

 described, in Porth Pridd (p. 237). The Llandeilo rocks are over- 

 thrust by slaty beds of the Llanbadrig Series with some quartzite, 

 and the latter in their turn are overridden by slates belonging to 

 the Green Series. 



The Llanbadrig rocks in this section only fringe the Bay, being 

 cut out inland by a transverse fault which brings them against the 

 Green Slates. Some of the usual slaty beds, with patches of lime- 

 stone and quartzite, and a quartzose sandstone with purple slaty 

 matrix, form a strip below the Llandeilo conglomerates of Mynydd 

 Pant-y-gaseg, but the group is soon faulted out to the east. All 

 that are now left of the Llanbadrig rocks in this direction are a few 

 masses of quartzite and limestone (the latter associated with black 

 shale), involved in the Green Series near Glan-y-don, Bull Bay. 



The exposures of Llanbadrig Beds east of the Hell's Mouth 

 Fault seem to confirm the sequence suggested for the western 

 part of the Complex. The highest horizons are seen on the 

 western side of Porth Wen Bay to be a quartzite underlain by 

 pebbly slates which pass down, through slates with some local 

 developments of quartzite, into quartzites and shales with sub- 

 ordinate limestone. On the eastern side and to the south of Porth 

 "Wen Bay are rocks of the Llanbadrig Headland type, including a 

 limestone apparently referable to the horizon of the Trwyn y Pare 

 Limestone, and some crush-conglomerates which are probably of 

 the same horizon as those at Trwyn y Pare. From a comparison, 

 of the exposures of the whole area the probable succession of the 

 strata comprised under the name of the Llanbadrig Series 

 appears to be as stated below, in descending order, the total thick- 

 ness being estimated at about 1000 or 1500 feet : — 



Bf. Quartzite. 

 ■ lie. Pebbly slates. 



Bd. Slates with grit and quartzite-bands. 



Be. Quartzites, shales, and some limestone (at Porth Padrig, etc.). 



Bb. Limestone (as at Trwyn y Pare). 



Ba. Grits and slates, usually shattered to a crush-conglomerate. 



This interpretation is not without its difficulties and is not stated 

 with complete confidence ; it is put forward rather as a working 

 hypothesis, which may be useful in correlating similar rocks in other 

 parts of Anglesey. A small patch of these rocks has been noticed 

 by the present writer along a line of fault south of Mynachdy 

 Lodge, near Llanfair-y'nghornwy, and it seems clear from the 

 d3scriptions of various writers on Anglesey geology that the Series 

 occurs elsewhere in the island. 



