BRITISH ISLES. 19 



The ridge of altered rocks at St. David's is referred with doubt to 

 the Laurentian. The Cambrian rest un conformably upon it ; and from 

 the lowest Cambrian upwards there is conformity. In ascending order 

 the rocks are as follows -.—Longmynd or Harlech Group : grits, purple 

 and green sandstones, slates, and conglomerates, 4000 feet thick ; some 

 of the beds are so much altered as to have been described as Greenstone. 

 Menevian Group : slates and flags, 000 feet ; lithologically this and the 

 preceding group are unlike, but pala3ontologically they are closely allied ; 

 together they form the Lower Cambrian. Lingula-Flatj Group : sand- 

 stones, shales, and black slates, 2000 feet. In N. Wales the group is 

 5100 feet thick, and has 3 divisions : — Tremadoc Rocks : earthy slates 

 and flaggy sandstones, nearly 1000. feet. The Lingula Flags and 

 the Tremadocs form the Upper Cambrian, at the top and bottom of which 

 there are palaeontological breaks. The Lower Silurian consists of the fol- 

 lowing divisions : — llesting conformably on the Tremadocs is the Arenig 

 Group^ in 3 divisions : Lower (represented by the " Upper Tremadoc" 

 in N. Wales), fine black slates and shales, 1000 feet, containing about 

 48 species of Graptolites : Middle, slates and flags, with thin bands of 

 sandstone, 1500 feet ; there are a few Graptolites in the lower beds, 

 Trilobites ttc. in the upper : Upper, resembling the Lower Arenigs, 1500 

 feet ; a rich fauna has recently been discovered in this division, very 

 like that of the Angers Slate in France, and Barrande's Etage D. 1 in 

 Bohemia, hitherto unrecognized in Britain. Llandeilo Group, in 3 

 divisions: — Zoiy^r, black slates interstratified with volcanic tuff", 500 feet; 

 a distinct fauna : Middle, black calcareous shales and flags, with lime- 

 stone in the upper part, over 800 feet : Upper, black slates, flags, and 

 flaggy sandstones, with interbedded traps, over 1000 feet. The Upper 

 and Lower Llandeilo vary much in thickness, owing to the intercalated 

 volcanic beds. The Lower Llandeilo occurs in N. Wales ; but the ex- 

 istence of Middle and Upper Llandeilo is not yet proved there, though 

 they probably occur. The author refers to the history of the rocks 

 which he classes as Lower Silurian, and claims that Sedgwick's term 

 of Arenig should be reintroduced, the beds described under that name 

 being quite distinct from the Llandeilo beds of Llandeilo and Bluith. 

 Lists of fossils are given, and the following new species are described, 

 all from the Arenig Group of St. David's : — Ampyx Salteri, Trinucleus 

 Ethendgei, T. liamsayi (and Lower Llandeilo), Illcenus Hughetii, lllcB- 

 nopsis ? acuticaudata, JEglina Boia, ^. ohtusicaudata, Barrandea Hom- 

 frayi, Placoparia camhriensis, Phacops llanvirnensis, Calymene IIop- 

 Jcinsoni, Dinobolus'? Iliclcsii, Davidson, Ophileta, sp., Pleurotomaria 

 llanvimensis, Bellerophon llanuirnensis, Theca caereesiensis, T. HarTc- 

 nessi, Conularia llanvirnensis, and Orthoceras caereesiense. W. T. 



Hicks, H. On the Occurrence of Phosphates in the Cambrian llocks. 

 With an Appendix on the Chemical Analyses of the llocks, by 

 W. H. Hudleston. Quart. Joum. Geol. Soc. vol. xxxi. pp. 368- 

 385, woodcut section. 



As the result of analyses the author states that certain beds in tho 



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