308 The Rev. Prof. BMe—Ba&e of the Sedimentary Series. 



1859. Bos etruscus? Falconer MS., cf. Palseontological Memoirs and Xotes, 



ii. p. 481. 

 1866. Bos (Bibos) etruscus, Rutinieyer, Yersuch einer natiirl. Geschichte des Rindes, 



etc. ii. p. 71, seqq. 

 1874. Bos etruscus, Forsyth Major, Nageriiberreste aus Bohnerzen Siiddeutschlands 



und der Schweiz, Palasontographica, ii. 2 (xxii.), p. 123. 

 1877-8. Bos (Bibos) etruscus, Riitimeyer, Die Kinder der Tertiaer-Epoche, Abhh. 



Schweiz, Palseont. Ges. p. 154. 

 1877-8. Leptobos Strozzii, Riitimeyer, ii., pp. 167, 168, 173, 175. 



1884. Bos elatus, Deperet, Nouvelles e'tudes sur les Ruminants pliocenes et quater- 



naries d'Auvergne (Bull. Soc. Geol. de France 3e serie, t. xii. p. 247). 



1885. Bos elatus, Lydekker, Catalogue of the Fossil Mammalia in the British 



Museum (Aat. Hist.), part ii. p. 19. 



The Ttodentia are for the present represented only by a large 

 incisor, referable to the genus Castor. 



VII. — On the Base of the Sedimentary Series in England and 



Wales. 



By the Eev. Prof. J". F. Blake, M.A., F.G.S. 



A S Dr. Callaway has asked in a recent Number of the Geological 

 JIJL Magazine x for the grounds on which I suggest that some of 

 the volcanic rocks of Shropshire may perhaps be classed as Cambrian, 

 I take this opportunity for bringing before your readers the present 

 state of the inquiry into the nature and classification of the earliest 

 sedimentary rocks in this country. This inquiry has been spoken 

 of by Dr. Callaway as the " Archaean controversy " ; but we must 

 not necessarily call everything that is earlier than the Cambrian 

 "Archasan," any more than in old days it was right to call every- 

 thing Precarboniferous "unfossiliferous greywacke"; nor should 

 the inquiry be considered a controversy in its present stage, but 

 rather a search for more accurate knowledge. 



Omitting the Charnwood Forest rocks, and the Caldecott ashes, 

 about which there is little definite to say, the areas in which 

 Precambrian rocks have been described are — 1. St. Davids; 

 2. Anglesey; 3. North-west Carnarvonshire; 4. Malvern; 5. Shrop- 

 shire ; 6. Devonshire and Cornwall. I propose to point out, accord- 

 ing to my view, our present state of knowledge, and the history of 

 its growth, in each of these localities. 



1. St. Davids District. — It appears that when this was mapped by 

 Prof. Earn say, before 1857, he recognized below the basal Cambrian 

 conglomerates, besides a mass of crystalline rock, a series of more 

 or less volcanic detritus and lavas, but that this recognition was 

 never published. In its place was the indication that the latter were 

 "altered Cambrian." In 1877, however, Dr. Hicks, considering that 

 the Cambrian conglomerates, from the nature of their contents, and 

 their apparent unconformity, indicated a greater break than had been 

 recognized by Prof. Eamsay, set to work to describe the underlying 

 rocks as distinct formations. He was also under the influence of 

 theories of metamorphism ; but whereas, in Prof. Eamsay's hands, 

 these theories had led him to consider lavas and ashes as the 

 1 Geol. Mag. Decade III. Vol. VII. p. 143, 1890. 



