310 THE CANADIAN NATURALIST. [Vol. vi. 



Green Mountains, I have found the rocks of Anglesea to offer 

 remarkable lithological resemblances. 



It may here be noticed that the gold-bearing quartz veins in 

 North Wales are found in the Menevian beds, and also, according 

 to Selvvjn, throughout the Lingula-flags. These fossiliferous 

 strata at the gold-mine near Dolgelly appear in direct contact 

 with diorites and chloritic and talcose schists, which ure more or 

 less cupriferous, and themselves also contain gold-bearing quartz 

 veins. [Mem. Geol. Survey, part 2, pp. 42 ; 45, and Siluria, 

 4th ed., 450, 547.] 



The Table on page 312 gives a view of the lower paleozoic rocka 

 of Great Britain and North America, together with the various 

 nomenclatures and classifications referred to in the preceding 

 pages. In the second column, the horizontal black lines indicate 

 the positions of the thve'e important paleontologic il and strati- 

 graphical breaks signalized by Ramsay in the British succession. 

 [xMem. Gtol. Survey, III, part 2, page 2.] In a table by 

 D ividson in the Ge.ologicnl Mugnzlne for 1868 [V. 305] showing 

 the distribution of organic remains in these lower rocks, he gives, 

 as the Festiniog group of Sedgwick, only the Dolgelly and Maent- 

 wrog 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 Sedg- 

 wick. This however is not the present grouping and nomencla- 

 ture of Sedgwick, nor was it his earlier one. So far as regards Mid- 

 dle and Upper Cambrian, this discrepancy is explained by the fact 

 already stated, that in 1843 Sedgwick proposed, as a compromise, 

 the name of Cambro-Silurian for his B da group, previously called 

 Upper Cambrian ; by which change the Festiniog or Middle Cam- 

 brian became Upper Cambrian. When the true relation 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 Festiniog group, in which sense it is still used by 

 Lyell, Phillips, Davidson, Harkness and Hicks. The Festiniog 

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

 included not only the whole of the Lingula-flags but the Upper and 

 Lower Tremadoc rocks. [Philos. Mag. IV. viii. 362.] 



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

 British rocks adopted by Sedgwick and by Murchison, is in sepa- 

 rating the Menevian or Lower Lingula-flags from the Festiniog, 



