Prof. T. Sterry Hunt — On Ca7nbnan and Silurian. 509 



and chloritic and talcose scliists, wlaicb. are more or less cupriferous, 

 and themselves also contain gold-bearing quartz veins. (Mem. Geol. 

 Surv,, part 2, pp. 42, 45 ; and Siluria, 4th ed., pp. 450, 547.) 



The Table on p. 510 gives a view of the Lower Palaeozoic rocks of 

 Great Britain and North America, together with the various nomen- 

 clatures and classifications referred to in the preceding pages. In 

 the second column, the horizontal black lines indicate the positions of 

 the three important palseontological and stratigraphical breaks 

 signalized by Eamsay in the British succession. (Mem. Geol. Surv., 

 vol. iii. part 2, p. 2.) In a table by Davidson in the Geological 

 Magazine for 1868 (Vol.T. p. 305), showing the distribution of organic 

 remains in these lower rocks, he gives, as the Ffestiniog group of 

 Sedgwick, only the Dolgelly and Maentwrog beds of Belt (the 

 Upper and Middle Lingula-flags) ; and makes of the two divisions of 

 the Tremadoc rocks a separate group ; the whole being described as 

 the Upper Cambrian of Sedgwick. This, however, is not the present 

 grouping and nomenclature of Sedgwick, nor was it his earlier one. 

 So far as regards Middle and Upper Cambrian, this discrepancy is ex- 

 plained by the fact already stated, that, in 1843, Sedgwick proposed, 

 as a compromise, the name of Cambro-Silurian for his Bala group, 

 previously called Upper Cambrian ; by which change the Ffestiniog 

 or Middle Cambrian became Upper Cambrian. When the true re- 

 lation between the Lower Silurian of Murchison and the Bala group 

 was made known, Sedgwick, as we have seen, re-claimed for the 

 latter his former name of Upper Cambrian ; but this had meanwhile 

 been adopted for the Ffestiniog group, in which sense it is still used 

 by Lyell, Phillips, Davidson, Harkness, and Hicks. The Ffestiniog 

 group, or Middle Cambrian, as defined by Sedgwick, however, in- 

 cluded not only the whole of the Lingula-flags, but the Upper and 

 Lower Tremadoc rocks. (Philos. Mag., iv. vol. viii. p. 362.) 



The only change which I have made in the groupings of the 

 British rocks adopted by Sedgwick and Murchison is in separating 

 the Menevian or Lower Lingula-flags from the Ffestiniog, and 

 uniting it with the Bangor group or Lower Cambrian. In this I 

 follow, with Lyell and Davidson, the suggestion of Salter and Hicks. 



In the third column, the sub-divisions are those of the New York 

 and Canada Geological Surveys ; in connexion with which the reader 

 is referred to a table published in 1863, in the Geology of Canada, 

 p. 932. Opposite the Menevian I have placed the names of its 

 principal American localities ; which are Braintree, Mass., St. John, 

 New Brunswick, and St. John's, Newfoundland. "With regard to 

 the classification of Angelin, it is to be remarked that although he 

 designates II. as Regio Olenorum, and III. as Eegio Conocorypharum, 

 the position -of these, according to Linnarsson, is to be reversed ; the 

 Conocoryphe beds with Paradoxides being below and not above 

 those holding Olenus. The Begio Fucoidarum in Sweden has lately 

 furnished a Brachiopodous shell, Lingtda monilifera, besides the 

 curious plant-like fossil, Eophyton Linnceanum. (Linnarsson, Geol. 

 Magazine, 1869, Vol. VL p. 393.) 



