586 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



three to four feet thick, and much jointed ; partings of falsely bedded 

 clayey shale occur, and the whole quarry is apparently much dis- 

 turbed. 



South of Hopcott the red sandstones comprising the structure of 

 Grabbist Hill all dip to the north and north-east, and continue to 

 do so until they reach the deep Wotton-Courtney valley, between 

 Grabbist and Croydon hills, where, along the course of the river, a 

 reversion of dip takes place, either through faulting or a depressed an- 

 ticlinal ; this chauge is in a direct line with the St.-Decumans fault on 

 to Quantock Head. This reversion and change is traceable from 

 Dunster to the Foreland and Lynton ; and the southern dip of these 

 sandstones constitutes them the base of the whole of the superincum- 

 bent Grits, Slates, and Limestones of West Somerset and North Devon : 

 in other words, these red sandstones underlie, and are conformable 

 to, and form part of (the natural base) the Lower Devonian grits 

 and slates of the North Devon area. 



4. Dunster to Dulverton. — Having endeavoured to show along a 

 given line that we have a natural and conformable base for the higher 

 or succeeding series of grits and slates, I will now trace the junction 

 and the changes of character on the line of dip in West Somerset, 

 both as regards the physical structure of the rocks and the palaeonto- 

 logical value of their fossils, and will do so over two areas, one south 

 of Dunster, viz. from Dunster to Dulverton, and the other east of 

 Dunster to the Brendon Hills, through Withycombe, Higher Eoad- 

 water, Nettlecombe, and Treborough. At Timberscombe, Bickham, 

 and Oaktrow, south-west of Dunster, the sandstones and grits retain 

 their character, but are more thinly bedded and more fissile than 

 those to the north, and the partings are more slaty. These beds are an 

 easterly extension of the second series of red grits exposed at Wood- 

 abay, Trentishoe, and the Hangman. Between Oaktrow and Ash well 

 a gradual change takes place in the lithological character of the sand- 

 stones ; the grit beds become thinner, and give way to thicker masses 

 of interstratified slaty rocks ; and at Cutcombe the change becomes 

 complete. We here lose the red grits and fine sandstones alto- 

 gether; the passage from arenaceous to argillaceous rocks being 

 complete. We have here, then, as at Combe Martin Bay, evidence 

 of the grits, sandstones, and slates of the Hangman group passing 

 insensibly into the secoud, or Ilfracombe series, and that in the 

 clearest manner. South of Cutcombe, on the ridge at Wheddon 

 Cross, we meet with the lowest series of limestones in the Ilfracombe 

 group, which are here lenticularly arranged masses of calcareous 

 matter, due chiefly to organic influence, and interstratified amidst 

 the slate. In places these limestones are of considerable thickness, 

 and are used both for building and agricultural purposes, especially 

 at Newland, Court Hill, and Luckwell ; they are also extensively 

 developed to the east of Croydon Hill, at Higher Broadwater, Lod 

 Huish, and Nettlecombe. Favosites cervicornis, Stromatojoora con- 

 centrica, and Cyathojphyllum, &c. occur in the limestone-bands at 

 Wheddon Cross and Luckwell. 



No mollusca were observed ; tbeir absence is somewhat remark- 



