234 Mr Williamson on the Distribution of 



c. Sandstone, sometimes containing Pecopter'is Williamsonis and Otopteris obtusa 1 foot. 



d. Tenacious blue siiale ; the lower part carbonaceous : in this seam all the 



beautiful Gristhorpe plants occur 4 feet. 



e. Impure coal 3 inches. 



f. Alternating sandstones, ironstones, and shales 25 feet. 



g. Irony nodules 1 foot. 



h. Hard granular bed, very much ironshot, especially at the fissures 8 feet. 



From the occurrence of the large tubercular spines of a Cidaris, of Avicula 

 Braamburiensis,and Belemnites compressus in the thin calcareous seam, (a) it 

 appears clear to me that the upper beds of the Bath oolite, which atCloughton 

 Wyke and White Nab are at least thirteen or fourteen feet thick (p. 231 

 from the top of a to/), are here diminished to three. If this opinion be correct, 

 all the mass of sandstones at this point, considered by Professor Phillips as 

 helongingto his Upper sandstone and shale, must necessarily be removed from 

 that series, and be considered as merely a local and subordinate division of the 

 portion of the oolites of Bath and Brandsby, to which the name of Great or 

 Bath oolite is more particularly applied ; and the beds (g') and (h) will form 

 the lower portions of the series thus removed. I should arrive at this conclu- 

 sion for several reasons. 1st. The occurrence of the three fossils above al- 

 luded to, which are not met with in the cornbrash of the Yorkshire coast, the 

 only other formation to which the calcareous bed (a) can be referred, are 

 found together in the upper beds of the Bath oolite ; 2ndly, the existence of 

 beds of sandstone filled with carbonaceous fragments, evidently belonging to 

 the upper sandstone and shale, resting upon the calcareous deposit, whilst in 

 the immediate neighbourhood, we find the cornbrash, surmounted by the 

 Kelloways Rock ; and lastly from the absence of the blue clay, upon which 

 the cornbrash of the vicinity reposes. 



These inclosed sandstones do not appear to extend more than two miles along 

 the coast ; and I suppose they thin out beneath the low water mark in some part 

 of Carnelian Bay, as at its northern extremity, or White Nab, we find the supe- 

 rior oolitic beds in their true position; whilst at its southern point, or Ewe Nab, 

 the ferruginous beds occur as at Gristhorpe. So small a portion of the super- 

 incumbent sandstones are here exposed, owing to the low cliffs being partially 

 covered with diluvial clay, and the beach with sand and gravel, that we can- 

 not compare them with the section at the opposite side of the bay. On the 

 south side of this point is a small dislocation, but from the limited space 

 between this ferruginous bed, and the spot where the cornbrash first appears 

 to the south, I should say that even here the sandstones are far less extensive 

 than at Gristhorpe. In the middle of Gristhorpe Bay a singular depression 

 of the superior rocks, sinks these measures far beneath the line of low water. 



