680 



developed ; containing the Llandeilo flagstone and other character- 

 istic calcareous and shelly bands. 



(2.) The sections north of the Berwyns, connecting Montgo- 

 meryshire with Denbighshire. The ascending series is described as 

 follows : — 



(1.) A series of beds several thousand feet in thickness, and ap- 

 parently forming a passage between the Upper Cambrian and 

 lowest portion of the Silurian System. 

 (2.) Bands of calcareous slate with numerous organic remains of 



the " Caradoc Sandstone." 

 (3.) Series of flagstones, more or less calcareous, with many or- 

 thoceratites and two species of cardiola, overlaid by, and as- 

 sociated with, irregular masses of roofing slate with a trans- 

 verse cleavage. 

 (4.) Flagstones and rotten slates, many parts in an imperfect 

 state of induration, and the whole surmounted by the Car- 

 boniferous Limestone. — Of the preceding section the lower 

 part of No. 3. is identical with the series of Long Mountain 

 in the Silurian sections of Mr. Murchison; but No. 4. is 

 mineralogically unlike any thing he has described, although 

 it has been found to contain some of the fossils of the Upper 

 Ludlow Rock. It appears from these details that the Silurian 

 System, although its subdivisions are obscure from the abs- 

 ence of the Wenlock and Ludlow limestones, is more fully 

 developed than in the group (No. 3.) of the great Cumbrian 

 section above described. 

 The author then briefly notices the slate rocks of Charnwood Fo- 

 rest, which he refers provisionally to the Upper Cambrian System ; 

 but from the imperfection of the sections and the absence of organic 

 remains, their exact place is not determined. 



SECTION FROM THE NORTH TO THE SOUTH COAST OF DEVONSHIRE. 



L North Devon section. — For details the author refers to a paper 

 by Mr. Murchison and himself, but enumerates the successive 

 groups for the purpose of adding some remarks, and of connecting 

 the system of Devon with that of Cornwall*. The ascending order 

 is as follows : 



(1.) A series of coarse arenaceous slates, not noticed in the for- 

 mer paper. 

 (2.) The calcareous slates of the river Lyn. 

 (3.) The coarse red flagstones, &c., of Exmoor Forest, and of the 



coast to the east of Combe Martin. 

 (4.^ The calcareous slates and limestone bands of Ilfracombe. 

 (5.) The contorted slate zone south of Ilfracombe. 

 (6.) The calcareous slates and irregular masses of limestone be- 

 tween the preceding group and the culm measures. 

 The whole of the preceding series is placed in the Upper Cambrian 

 System with the exception of the upper portion of No. 6., which is 

 * See Proceedhigs, p. 556 et seq. 



