608 PEOCEEDINGS OF THE GEOLOGICAL SOCIETY. 



of this group and area, from its important bearing upon the question 

 at issue, and also for my purpose when I enter upon the palseon- 

 tological value of the fossils in the several groups, and also because 

 there has never been any satisfactory notice of the sequence and 

 associated fossils of the Ilfracombe group. Apparently they have 

 been much overlooked ; and it is Mr. YaljDy's collection that now 

 supplies the mass of authenticated species, by which, with my own 

 observations and the examination of his collection, I am enabled to 

 make the somewhat complete accompanying list. Professor Phillips* 

 names 37 species as occurring in the Ilfracombe group in North De- 

 von ; one Brachiopod, viz. String ocepTialus Burtini, seemed then to 

 have been the only known form in that area. Through the labours 

 of Mr. Valpy I am now enabled to add between 50 and 60 species 

 to this Middle Devonian or Ilfracombe group alone, so that we have 

 here (in North) as in South Devon, and the three typical areas in 

 Europe, a Middle Devonian fauna of great and important value. 



4. Ilfracombe District. — Although a traverse was made from Hed- 

 don's Mouth to Pilton, via Paracombe and Kentisbury, across all the 

 series to the south, which I have described at pp. 601-604, 1 still de- 

 sire to describe tersely the one made from the sea, at Ilfracombe, to the 

 Muddiford valley, via Bittadon, to examine the igneous rocks of 

 that place, it being here that the best known exposure of porphy- 

 ritic felstone occurs, which so nearly resembles the Hestercombe 

 granite — so called — on the Quantock Hills f both in character and 

 stratigraphical position, occupying in both areas the upper part of 

 the Morle slates, or base of the Upper Old Eed Sandstone (Piek- 

 weir Sandstones), and recognized at places between these two points, 

 and again at Morte Bay. The exposure at Bittadon, although small, 

 is important, the rock being apparently a contemporaneously 

 bedded, coarse-grained, stratified, felstone porphyry, the crystals of 

 felspar being in a green felspathic paste. 



The sections exposed in the slates up the steep and winding road 

 leading from Ilfracombe to Two- Post Turnpike-gate are such as are 

 known all through this lower portion of the Ilfracombe or Combe- 

 Martin group — waved, undulating, contorted, and cleaved beds of 

 slate with bands of impure limestone containing but few fossils. 

 After passing the Chambercombe limestone we enter a tract of coun- 

 try almost void of calcareous matter, the meridian of Kentisbury, 

 an exposure west of Ilfracombe being the highest known definitely 

 marked limestone zone. South of this, the slates alter in colour and 

 character, becoming indurated and more thickly bedded, assuming a 

 brown or yellowish tint, and are quarried for building-purposes ; 

 roofing-slates are quarried at Woodscot &c. 



The mean dip of the slates from the sea at Hagginton beach to 

 Bittadon, over a space of eight miles, is about 40° S.S.W., with 

 cleavage -planes to the south at high angles. It is along the meri- 

 dian of Bittadon, West Down, Woolacombe, and Arlington &c. that 

 Professor Jukes believes his concealed and hypothetical downthrow 



* Pal. Foss. Cornwall and Devon, 1841. 

 f Leonard Horner. 



