Vol. 52.] ASSOCIATED BEDS, IN N. DEVON AND W. SOMERSET. 265 



succession of the rocks in North Devon will come in more appro- 

 priately after the second part of the paper, which will contain 

 the evidence obtained from other areas, has been read before the 

 Society. 



The changed position now given to the Morte Slates removes one 

 of the greatest difficulties experienced by previous writers in their 

 attempts at correlating the strata in North Devon with those in 

 other areas, for nowhere else had such a thick series of well-cleaved 

 slates been met with at the horizons assigned to them here. The 

 horizons necessarily varied in accordance with the views in regard 

 to the succession held by the authors. Those who held with Prof. 

 Jukes that there was but one group in North Devon of sandstones, 

 slates or shales, and calcareous beds, repeated by faults, found it 

 necessary to place the Morte Slates at the top of the whole series ; 

 while those who claimed that there were two or more series of 

 somewhat similar sediments conformable to one another placed them 

 not far from the centre in the succession. There is good evidence 

 at many points to show that Prof. Jukes was correct in claiming 

 a faulted junction between the Morte Slates and the Pickwell Down 

 Beds, but the results produced by the faults are different from those 

 which he suggested ; for, instead of one great broken trough with the 

 Pickwell Down Beds coming up from under the Morte Slates, we 

 find the former resting upon the latter, the faults between being 

 due to crushing during the movements which brought the Morte 

 Slates and the Pickwell Down Beds to the surface. 



Until the thrust-fault between the Morte Slates and the llfra- 

 combe Beds on the northern side had been made out, the only way by 

 which a repetition of the beds could have taken place would be by a 

 great fault on the southern side ; but this would necessitate a much 

 greater displacement of the beds than by that which is now 

 known to occur on the northern side of the Morte Slates. 



The discovery of fossils in the Morte Slates belonging to several 

 horizons in the succession, and some probably as low in position as 

 the base of the Silurian (Upper Silurian of the Geological Survev), 

 added to the stratigraphical evidence, enables us now to speak with 

 confidence as to their place in the succession in North Devon. They 

 are the oldest rocks in the area, and they do not appear to contain 

 amongst them any beds newer than Lower Devonian. In some 

 places newer rocks may occur amongst them as the results of faults 

 or unconformities, but not in order of succession. 



In the second part of the paper evidence will be given to show 

 that in at least one of the areas examined there appears to be a 

 passage from some of the Morte Slates to Lower Devonian rocks 

 containing so characteristic a fossil as Phacops (Cn/p7ia>us) lac'mi- 

 atus. These passage-beds lie on the southern side between fairly 

 typical Morte Slates and Pickwell Down Sandstones, and in the 

 latter, quite near one of the junctions, we discovered a band rich in 

 fossil wood, and other evidences indicating that the}* had been 

 deposited near land. When an interpretation of the succession in 

 North Devon and West Somerset, in accordance with the evidence 



