404? Geological Society. 



of age, and the term greywacke being lithologically applicable 

 to beds of every class of rocks, and as Devonshire affords the 

 best type of the fossils of this intermediate system, the authors 

 propose to substitute the term Devonian for old red sandstone; 

 and they hope that the organic remains, discovered in that county, 

 "will enable continental geologists to detect in their own country, 

 a system of strata hitherto supposed to be almost peculiar to the 

 British Isles. 



The authors acknowledge the assistance they have received from 

 Mr. J. Sowerby ; and that Mr. Lonsdale first suggested, from their 

 fossil contents, that the limestones of S. Devonshire might prove to 

 be the representatives of the old red sandstone. 



A paper was afterwards read on the structure of South Devon, by 

 Robert A. C. Austen, Esq., F.G.S. 



This communication is supplementary to a memoir read in 1837 *, 

 and its object is to show the general relations of the various bands 

 of slates, limestones, and sandstones in South Devon. 



Commencing with the older deposits east of the Teign, there ap- 

 pear — 



1st. Slates, but of which little is seen. 



2nd. A band of black stratified limestone of variable thickness 

 and slaty structure. It contains much carbonaceous matter, thin 

 seams of anthracite, also corals and Brachiopoda. It is associated 

 with irregular beds of contemporaneous trap. The band is stated to 

 range from Staple Hill on the east, through Bickington, Ashburton, 

 Buckfastleigh, and Dean, near which the limestone ends ; but the 

 calcareous slate and limestone of the south of Cornwall, Mr. Austen 

 considers to be of the same age. These beds dip south. 



3rd. Fine-grained schists and roofing slates. 



4th. The Plymouth limestones, which cannot be traced west- 

 ward further than Whitesand Bay, but to the eastward they are 

 considered by Mr. Austen to be represented by the limestones of 

 Dunwell, Shilstone, Ugborongh, Fowley- cumber. North Huish, Sto- 

 verton. Great and Little Hampston, &c. 



5th. An arenaceous deposit, often coarse and resembling old 

 red sandstone ; but sometimes conglomeratic, and then not distin- 

 guishable from the new red of Devonshire. Its upper conglomeratic 

 portion ranges from Plymouth Sound and Bigbury Bay, to Modbury 

 and Blackdown ; its lower portion cuts the Dart a little below Tot- 

 ness, and rises into lofty hills, east of a line passing through Berry 

 Pomeroy, Marldon, Cockington, and Barton. It contains limestone 

 south of Yealrapton, and at Sequers Bridge ; also several thin 

 bands on the Dart, and beds at Berry, Marldon, Collaton, and Yal- 

 berton. Organic remains are not uncommon in this arenaceous di- 

 vision. Only the fine-grained beds show a slaty cleavage. The 

 limestone is confined to its northern limit, and has a southwardly dip ; 

 but all the lines of roofing slate are to the southern with either ver- 

 tical or northern cleavage dips. As the intermediate country about 



• Proceedings, vol. ii., p. 584. [or L. & E. Phil. Mag., vol, xiii. p. 664. 



—Edit.] 



