648 Professor Sedgwick, and R. I. Murchison^ Esq.^ on the 



siliceous sandstone, resembling those last described, continue for some way as we ascend the hill 

 which runs out into Baggy Point. Gradually, however, the alternating glossy slates almost dis- 

 appear, and the strata put on the form of gray and brownish gray micaceous flagstones ; and asso- 

 ciated with them, near the top of the hill, are some cellular ferruginous bands, with numerous 

 obscure casts of fossils. 



Doubling Baggy Point and descending to the north side of Croyde Bay, slaty masses again 

 abound, which, though very fossiliferous, and of much more earthy texture than those of the 

 preceding group, have generally a true slaty cleavage. These cleavage-planes strike very nearly, 

 though not always exactly, with the beds ; and in this part of the coast they generally incline at 

 a high angle towards the north, the prevailing dip of the strata being towards the south. 



Phenomena of this kind are always instructive, and are more especially so on the coast of 

 Santon Down, where the beds are highly fossiliferous and thrown into a succession of undulations. 

 In this part of the coast, many of the rocks conform so nearly to the mineral type of the lower 

 division of the Silurian system, that the descriptions of the slaty varieties of the Caradoc sandstone 

 of Shropshire and Herefordshire might be applied to this Devonian series, almost word for word. 

 The lower or middle portion of the group, we are describing, may be easily followed along its 

 strike into the interior of the country ; and there are two quarries in it which deserve notice. One 

 of them, first noticed by Major Harding, is near the inn by the road-side at Marwood, and ex- 

 poses a set of strong beds of brownish gray and greenish gray sandstone; at the partings of which 

 are several ferruginous, cellular, and earthy bands with numerous casts of fossils. The other is at 

 Sloly, nearly three miles north of Barnstaple, and close to the turnpike road. It deserves notice 

 from the structure of its coarse and thick beds of greenish gray and brownish gray sandstone, 

 separated by the bands of earthy slate and shale ; and still more from the vegetable fossils disco- 

 vered in it by Major Harding and the Rev. D. Williams, which will be described in another place. 

 In both the above quarries the dip is almost south ; but a little nearer Barnstaple, similar beds 

 are reversed and thrown into undulations. 



Lastly, the highest portion of our present group passes into a deposit of soft and rather earthy 

 slates with subordinate bands of sandstone, and occupies generally a low tract of country skirt- 

 ing the northern boundary of the culm measures. It is very fossiliferous, and sometimes highly 

 calcareous, passing, as before mentioned, into irregular masses (or junks) of limestone. These 

 however, are seldom worked, in consequence of the immediate vicinity of the great open quarries 

 of black limestone, found in the lower portion of the overlying formation. 



In consequence of the undulations above noticed, and of the interruptions caused by the wide 

 marshes bordering on the Barnstaple river, it is very difficult to make any approximation to the 

 whole thickness of this group. We have, however, evidence enough to show, that the thickness 

 must be very great, without taking into account the lower undulating masses. Beyond Dul- 

 verton, in its range towards the plain of the new red sandstone, it becomes much more ferru- 

 ginous, and is greatly modified in mineral structure, as we have already pointed out. 



Among the fossils of the lower part of this group (Marwood quarries) are shells of the genera 

 Cucullcea, Cypricardia, and Bellerophon, One species very closely resembles Bellerophon globu- 

 lus of the old red sandstone. Nearly on the same line (Sloly quarry) occur the vegetable impres- 

 sions above noticed. By far the greatest number of fossils occur, however, in the upper part of this 

 group ; and among them, we noticed innumerable crinoidal stems, many fragments of Trilobites, 

 Orthoceratites, Terebratulae, many Spirifers, a few spined Productse, &c. &c. A more detailed 

 account of these fossils is reserved for a future communication. 



