664 MR. C. A. MATLET ON THE [^^g* 1 899, 



of typical crush-conglomerate, which consists of a dull slaty matrix 

 full of grit-bands more or less broken into fragments. Some of the 

 bands can be followed unbroken along the strike for quite 8 feet, 

 but they are mostly broken up into isolated pieces, the majority of 

 small size. I measured some, however, having the following dimen- 

 sions : — 5| by 3 feet ; 6| by 2 feet ; 6 by 2^ feet. These larger 

 inclusions were more or less lenticular in outline, and had the 

 longest axis in the direction of the line of strike. They showed 

 very little alteration ; but the matrix of this crush-zoue displays 

 the typical micro-structures of crush-rocks, corresponding in all 

 essential respects with the Isle of Man examples. 



The main limestone-mass, — that of Trwyn y Pare, in which the 

 basin-like-folds noticed earlier in this paper (p. 652) occur — is now 

 reached. It forms a band some 250 yards broad, beyond which is 

 another tract of rocks similar to those on Cemaes shore. Though the 

 beds are still broken up, the cataclastic derivation of the quartzite- 

 lumps may be clearly inferred from their frequent occurrence as 

 series of more or less connected lenticles. 



Pig. 11. — South-eastern corner of Cemaes Bay : parts of hroTcen 

 quartzite-hands. 



[The upper band is 3| feet, the lower 4^ feet, in length.] 



Continuing from this point along the shore of Perth Padrig, we 

 come upon a large development of bedded grit and quartzite inter- 

 stratified with pale yellow and sage-green, felspathic, shaly, and gritty 

 mudstones, an occasional patch of limestone, and some Llandeilo 

 black graptolitic shales. The thickness of individual beds is often ex- 

 tremely irregular, and the whole of this section has evidently under- 

 gone much movement. At Llanbadrig there is another development 

 of limestone and quartzite among grey and reddish slaty beds. The 

 harder rocks are very much crumpled up among the softer ones, and 

 pieces of quartzite and limestone have become detached and lie 

 isolated in the slates. The structure appears to be somewhat similar 

 to that noticed at Penrhyn, though the disruption is not so complete. 

 Many of the bands can be readily traced, others are very irregular, 

 and we find all stages from strings of lenticles to ' pebbles.' The 

 quartzite-masses are much brecciated : some even seem to be made 

 vip of cemented fragments. 



