Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/549

 fended the Survey nomenclature by reference to the then received definition of Syenite and Greenstone, terms still imperfectly understood and applicable to the main mass of the rocks in question, though possibly subsequent closer examination and new sections may have rendered some modification of the boundary line desirable. He was prepared to allow the metamorphic origin of all rocks of the classes under consideration, but did not think there was sufficient evidence to show that the divisional planes in the Syenite and Greenstone of St. David's were due to original stratification ; but they might correspond rather to the great joints of most granites. Mr. Hughes pointed out that the conglomerate contained fragments of the hornstone and quartz of this older series, which he considered was probably part of an old ridge or shoal, possibly of Laurentian, but certainly of Pre- Cambrian age, and thought that there were slight differences in the lithological character of the beds on either side, such as might be explained on this supposition. He agreed with Prof. Ramsay in thinking that there was evidence of the proximity of land in early Cambrian times, but was not prepared to refer these red rocks to inland seas or lakes as opposed to open sea ; the whole seemed rather the deposit of an open sea encroaching during submergence. He did not attach very much importance to the restriction of genera to limited horizons in these older rocks of St. David's ; for, as it was reserved for Mr. Hicks to discover these fossils after so many other observers had examined the district, he anticipated that further researches must certainly result in finding links which will connect together more closely beds the stratigraphical relations of which seem to indicate so clearly an unbroken though varying series.

Mr. Gwyn Jeffreys had been struck by the intercalation of non-fossiliferous beds from time to time among the fossiliferous beds described in the paper. Beds now in course of formation contained also very few, if any, organisms, apparently in consequence of the great deposits of mud brought down by rivers and redeposited in certain parts of the sea-bed. That this was the case had been proved by recent dredging- operations both in the Atlantic, off the coast of Spain, and in the Mediterranean.

Mr. Boyd Dawkins called attention to the extension of the Molluscoida, Annulosa, and Mollusca, deep down in the Cambrian rocks, and yet without any trace of their convergence. The origin of life might be as far removed from that period as was the Cambrian from the present time. The difference in the colours of the rocks he was inclined to refer to the different degrees of oxidation of the iron they contained, which might supervene in a comparatively short time.

The Rev. W. S. Symonds had, in visiting the spot, been much struck by the rocks, at that time termed Syenite, which he believed might be an extension of those on the Carnarvonshire peninsula, and which he thought supported the whole series of the Cambrian rocks, so that they might after all be the Laurentian, the same as

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