J. B. Hill — The Palceozoics of Wed Cornwall. 213 



prevailing strike, but also in lithological type and metamorphic 

 condition. For these reasons they are taken to represent the base- 

 ment beds of that formation. 



Relative deformation of the Older and Newer Palceozoics. 



It has already been pointed out that the Lower Palaeozoic rocks 

 exhibit a greater degree of deformation than do the overlying 

 Devonian. It can be shown by the included boulders in the Devonian 

 conglomerate that the Caradoc quartzite was brecciated and the 

 interstices cemented by silica prior to their incorporation in that 

 deposit. It has likewise been shown from the same evidence that 

 the Portscatho Beds had been welded into solid rock and veined with 

 quartz before the formation of that conglomerate. The Lower 

 Pal£eozoic beds, therefore, must have been buried deep within the 

 crust and compi-essed into solid rock, and subsequently upheaved to 

 form the floor of the Devonian seas. At the close of the Carboni- 

 ferous period these rocks, in common with the overlying Devonian, 

 were again brought within the influence of crustal disturbance, by 

 which they were folded, fractured, and cleaved. As a result of this 

 twofold experience in the subterranean depths almost all traces of 

 organic life appear to have been obliterated. So far as the Mylor, 

 Falmouth, and Portscatho divisions are concerned, and even the 

 Veryan Series if we exclude the quartzite, the sole relic of life that 

 has survived, except an occasional crinoid fragment, is confined to 

 the Kadiolaria, the preservation of their casts being in no small 

 measure due to the minuteness of these tiny creatures, and to the 

 siliceous nature of the cement in which they are usually encased. 



Age of the Lower Palceozoic divisions. 



The age of the Lower Palaeozoics cannot be precisely defined. 

 The Quartzite is of Lower Silurian age, and palaeontologists are 

 agreed that the fauna is Caradoc.^ If its inclusion in the Veryan 

 group be correct — and there is no evidence at present pointing to 

 a discordance in the sequence — there is a natural succession from the 

 Quartzite on the one hand to the Mylor Series on the other. The 

 discovery of Upper Silurian fossils by Messrs. Upfield Green, 

 Sherborn, and Eeid in areas closely adjoining to the Caradoc 

 Quartzite would appear to indicate a downward succession, of which 

 the Mylor Series represents the base, and that the Lower Palaeozoic 

 divisions referred to in this paper are Lower Silurian. As the 

 survey, however, of the older Palaaozoics in the Meneage peninsula 

 has not yet been completed, it will be safer to defer further con- 

 sideration of this subject until the evidence has been exhausted. It 

 will be sufficient for the present to have demonstrated the limits of 

 the Devonian, and to have shown that the killas of West Cornwall 

 is chiefly restricted to the Lower Palaeozoics, of which at least one 

 member is of Caradoc age. 



^ The Lower Silui-ian age of this quartzite was proved by the late Mr. Charles "W. 

 Peach, to whose palaeontological researches Cornish geology owes so much. 

 Mui'chison noted that the Gorran fossils were Upper Caradoc, and those of Gerrans 

 Bay (Came quartzite) were even younger (Trans. Eoy. Geol. Soc. Cornwall, vol. vi). 



