Dr. PiTTON on the Strata below the Chalk, 233 



Devonshire. 



(118.) The coast on the west of Portland as far as Sidmouth has been 

 described by Dr. Buckland and Mr. De la Beche * in these Transactions ; 

 where also the former has published a map of the coast between Teignmouth 

 and Portland, with views from Sidmouth to Bere Head, and from Lyme Regis 

 to the vicinity of Weymouth and Portland f. The coast of Devonshire, 

 therefore, requires no additional illustration ; and for the local extent and 

 distribution of the strata in the interior of that county, it is now in my power 

 to refer to the beautiful Geological Map recently completed by Mr. De la 

 Beche];, and to be followed by an explanatory memoir and sections. 



As the beds between the chalk and the bottom of the lower green-sand on 

 the west of Purbeck appear to have coalesced, and are no longer marked by 

 the previous subdivisions, the green-sand of Devonshire may be regarded as 

 the equivalent of the whole series. The lower green-sand seems especially 

 to have been reduced in bulk, in its progress westward. The gault has 

 wholly disappeared ; but some of its characteristic fossils are found in the 

 sand and grit of the cliffs on the west of Lyme. At the bottom of the 

 sands the boundary is everywhere distinct : and the plateau which shoots 

 out to the west of Dorsetshire is found successively in apposition with the 

 lower oolite, the lias, and new red sandstone ; while its remotest portion rests 

 on grauwacke slate. Throughout the greatest part of the tracts thus occu- 

 pied, the green-sand forms a flat-topped, uniform cap, investing the hills, as 

 far west as Sidmouth on the coast, and the Blackdown range on the north 

 of that place, nearly to Wellington ; and finally, it constitutes an exten- 

 sive outlier, from the north-west of Teignmouth to Penhill, about six miles 

 south-west of Exeter, which caps the heights of Great and Little Haldon, 

 and is detached from the more continuous tract above mentioned by an 

 interval of more than twelve miles, occupied by the new red sandstone. 



Several insulated portions of chalk, however, still remain above the eastern portion of the 

 green-sand platform, especially upon the coast between Sidmouth and Lyme, and along the line 

 from Beaminster through Chard and White Stanton. The transition from the chalk to the sands 

 is well seen at some of the junctions, especially on the south-west of Axmouth, where the strata 



* See their joint memoir at the commencement of the present volume ; Geol. Trans., 2nd 

 Series, vol. i. p. 40, &c. : and a separate paper by Mr. De la Beche, vol. ii. p. 109, &c. 



t Ibid:, vol. i. p. 95, &c. 



J " Ordnance Geological Map of Devon, and of portions of Cornwall and Somerset, by H. T. 

 " De la Beche, Esq.," in eight coloured sheets. 



2h2 



