30 THE GEOLOGY OP JVIY2^YDD-Y-GARN. [Feb. I9OI, 



of an isolated mass almost everywhere bounded by faults. The 

 difference also of the breccia-conglomerate here from the pebbly 

 conglomerate a little farther north is very remarkable. Much of 

 the older rocks hereabouts and to the south are breccias ; some of 

 them are crush-breccias, w-hich are local ; but most are originally 

 eruptive, though squeezed later. The speaker thought that the 

 pisolites here would be found to repi'esent a definite horizon, like 

 those in the Lleyn and near Bettws Garmon. 



Prof. Watts also spoke. 



The AuTHOK thought that very little reply was needed. The 

 pisolitic iron-ore of the mainland of Wales, according to the text- 

 books, is of Arenig age, while the oolitic ironstone of the northern 

 part of Anglesey is assignable to the Llandeilo. 



