{ Lower Devonian Lower Devonian { Hangman Grits { Slates (Coblenzian) { Lynton Slates { Lincombe and Warberry { Foreland Grits { Grits and { Meadfoot Sands [Footnote 83: An account of the South Devon rocks by Mr Ussher will be found in the _Quart. Journ. Geol. Soc._, vol. XLVI. p. 487; from it the above classification of the rocks of S. Devon is taken.] The division into Lower Middle and Upper Devonian is generally adopted, though the alternative titles given to these divisions are not always used with the same signification, and the distribution of the different local stages given in the above classifications is usually adopted in the main, though a detailed comparison of the Devonian beds of North and South Devon is still attended with difficulty. More than once an attempt has been made to prove that the apparent succession of the North Devon rocks, which is that given in the above table, is not the true one, and of recent years Dr Hicks has obtained a number of fossils from the Morte Slates which had hitherto yielded none, and he believes that these fossils indicate that the Morte Slates are on a lower horizon than the beds on which they rest. Whatever be the ultimate verdict, we can, at any rate, say that the "Devonian Question," as it is termed, is not settled[84]. [Footnote 84: See Hicks, H., "On the Morte Slates and Associated Beds in North Devon and West Somerset," _Quart. Journ. Geol. Soc._, vols. LII. p. 254, LIII. p. 438.] _Description of the Strata._ The general variations in the lithological characters of the deposits of Devonian age will be seen from the accompanying figure which represents the deposits of Britain as they occurred from north to south before they had been affected by subsequent earth-movements (Fig. 19). The conventional signs which are used are similar to those which have been used in other parts of this work, and will save description of the section. [Illustration: Fig. 19. A. Lower Palæozoic and Precambrian Rocks. N.S. North of Scotland } C.V. Central valley of ditto } Old Red Sandstone Type. W. Wales } N.D. North Devon } Devon Type. S.D. South Devon } ] The ridges separate different deposits of Devonian rocks, which were possibly deposited in isolated areas, though there was probably connexion between them at any rate at times.