88 



Carnarvon to Garth Point near Bangor. The pebbles vary 

 according to the rocks on which the conglomerate locally rests ; 

 near Carnarvon they are chiefly quartz, near Llanddeiniolen and 

 near Bangor they include pebbles of quartzite, andesite, felsite, and 

 quartz. 



Sir A. Ramsay was of opinion that the whole of the Lingula 

 flags had thinned out near Bangor, that the grits were of Harlech 

 age and were overlain unconformably by Arenig shales. This, 

 however, is not the generally accepted view, for there is no evidence 

 of such unconformity, and if the diminution of thickness is due to 

 thinning out toward a shore line we should expect the lower beds 

 to thin out and disappear before the upper beds. The facts may be 

 explained as a simple case of overlap, and we may suppose that the 

 whole of the Harlech Series (i.e. Lower and Middle Cambrian) has 

 thinned out with probably some of the Lingula slates (Maentwrog 

 Beds), and that the lowest Cambrians between Llanddeiniolen and 

 Bangor represent the Lingula grits of Elidyr-fawr and Marchlyn- 

 mawr. They may, however, be of still later date. 



Whether Tremadoc Beds exist to the north-west of Snowdon 

 has not yet been ascertained because of the scarcity of fossils in 

 the mass of dark slates which intervenes between the Lingula grits 

 and the Arenig grits. 



2. Midland Counties 



Cambrian rocks are brought to the surface in four distinct and 

 isolated areas in the Midlands, viz. (1) Malvern Hills, (2) The 

 Wrekin (Shropshire), (3) the Lower Lickey Hill (Worcestershire), 

 and (4) Nuneaton (Warwickshire). In lithological characters, and 

 to some extent also in their fossil contents, these Midland rocks 

 differ very much from the typical Cambrian of Wales, and accord- 

 ing to Professor Lapworth 12 they approximate more closely to the 

 Cambrian of Scotland and of the continent of Europe. The total 

 thickness of the system is very much less in the Midlands than in 

 Wales, and though it is believed that in the western areas the 

 succession is incomplete, it appears to be unbroken near Nuneaton, 

 where the thickness of the exposed beds is only about 2200 feet, 

 and if 800 feet are added for the concealed upper beds, the total is 

 then only 3000. The whole system is divisible into a lower 

 arenaceous division, comparable to the Caerfai and Solva Beds of 

 South Wales, and an upper shaly division, representing the Lingula 

 flags and the Tremadoc Beds. 



The Arenaceous Division. At the south-west end of the 

 Malvern Hills the Archaean schists are bordered by beds of quartzite 



