2QS VnOF. E. HULL ON THE GEOLOGICAL RELATIONS 



The Lower Devonian beds of Belgium were deposited against a 

 shelving shore formed of Lower Silurian rocks, the Upper Silurian 

 beds being absent : hence these beds are often in the form of con- 

 glomerates, belonging to different geological horizons, deposited 

 against the shores of '^ the Crete du Condroz"*. 



X. The Botjlonnais. 



Of the numerous descriptions of the Palaeozoic series in the Bou- 

 lonnais, the latest is that by Dr. Charles Barrois f, who has given a 

 very clear statement of the succession of the beds from the coal- 

 measures of Locquinghen down to the lowest beds of the Devonian 

 series as there represented. A brief resume maj' here be useful, 

 together with an indication of the representative beds in North 

 Devon. 



Section of the Palceozoic Series of the Boulonnais. Synonyms. 



Coal-measures of Locquinghen. 

 Hardinghen Sandstone (Millstone Grit). 

 ["Limestone with Prodicctus gigaoiteus. 

 Carboniferous J Napoleon marble, P. undatus. 

 Limestone. 1 Haut-banc Limestone, P. cora. 

 [^Dolomite, with Crinoids. 

 ( 



Fiennes Sandstone, with CiicullcBa 



'Upper part : Marwood 

 beds, or Coomhola 

 Grits. 

 Lower : Pickwell-down 

 Sandstone. 



Middle 

 Devonian. 



Hardingii. 

 Upper ^ -^^^ (.j^y^ ^^^ ^ht^lQs. 

 13evonxan. , ^^^,^^^^ Limestone, Spirifer Ver- Y ^^^^^.^^ ^^ 

 neuiLi. J 



Shales of Beaulieu and Dolomite 



of Nores. 

 Blacourt Limestone, Orthis stri- "1 Calc. de Givet, or Ilfra- 



atula. J combe beds. 



Conglomerates, red Shales and 1 



green Sandstones of Blacourt. I Hangman Grits, &c. 

 Ferns and Calamites. J 



Lower Devonian absent. The Lower Silurian beds underlie the Middle 

 Devonians. 



XI. Eepresentative Beds op South Wales and the 

 Welsh Borders (Eegion op Siluria). 



It is insisted upon by nearly all writers that on the borders of 

 Wales, near Ludlow, there is a perfect conformity and actual pas- 

 sage from the uppermost Silurian into the lowermost beds of the 

 Old Eed Sandstone J (or " Cornstone formation"). While this is 

 allowed to be the case in the direction of Shropshire, it is hinted by 

 Sir B. I.Murchison§ that in Brecknockshire, Caermarthenshire, and 



^ On this subject, see the papers by MM. Cornet et Briart, Ann. Soc. Geol. 

 de Belgique, t. iv. 



t Proc. Geol. Assoc, vol. vi. ; also Sir R. Murchlson, 'Siluria,' p. 411, 4th 

 edit.; Mr. Godwin- Austen, Quart. Journ. Geol. Soc. vol. ix. p. 231, &c. 



I De la Becbe, Mem. Geol. Survey, vol. i. p. 50 ; Ramsay, Pbys. Geol. and 

 Geogr. of Great Britain, 5th edit. p. 104 ; Murcliisou, ' Siluria', 4th edit, 

 p. 246. § Ibid. p. 247. 



