English Stratified Rocks inferior to the Old Red Sandstone. 305 



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

 remains, their exact place is not determined. 



SECTIOJf FROM THE NORTH TO THE SOUTH COAST OF DEVONSHIRE. 



I. 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 

 considered, both from its structure and its fossils, as near the doubt- 

 ful limit between the Upper Cambrian and Lower Silurian Systems. 



II. Culm measures. — This series is described (as in a former paper) 

 to occupy a great trough, which ranges across the country in a di- 

 rection bearing nearly east and west ; on its north side overlying 

 the preceding group (No. 6. of the North Devon section), and 

 on its south side rising up to the granite of Dartmoor, or overlying 

 the older slate system of Devonshire 'and Cornwallf. Its subdivi- 

 sions are enumerated as in the former paper ; and the author adds, 

 that during the summer of 1837 he ascertained that the lower beds 

 of the culm measures rest unconformably on a portion of the slate 

 rocks in the north of Cornwall, near Launceston. On the contrary, 

 in the cliffs near Barnstaple, the lower culm measures seem to gra- 

 duate almost insensibly into the formation on which it rests. Hence 

 (independently of all other evidence) it is clear that the slate rocks in 

 the north of Cornwall are of an older epoch than the upper group 

 of the North Devon section. 



The author then considers the classification of the culm series, and 

 states his opinion that the base of it is lower than the base of the 

 ordinary English carboniferous series. The base line (in the former 

 jiaper) was intentionally left in an ambiguous position ; and the dif- 

 ficulty of the subject has been subsequently increased by the supposed 

 discovery of some true carboniferous plants in the highest group 

 (No. G.) of the North Devon section. In the upper part of the culm 

 measures all the fossil plants have been described as identical in spe- 

 cies with plants of the carboniferous series ; and hence (unless some 



* See Proceedings of Geological Society, vol. ii. p. 55G et seq, [or L. & 

 E. Phil. Mag. vol. xi. p. 311.] 



t See Proceedings, vol. ii. p. 561. [L. & E. Phil. Mag. vol. xi. p. 315, 316.] 

 Phil Mag. S. 3. Vol. 13. No. 82. Oct. 1838. X 



