322 J. F. BLAKE AND W. H. HUDLESTON ON 



The oolite of the Lower Limestone (d) is fully seen in the 

 "White Quarry," where, exclusive of the impure limestones assigned 

 to the preceding group, it has a thickness of about 33 feet, measured 

 to a projecting sheet of impure broken-shell limestone, which forms 

 the base of the " Intermediate Series." It is rather unfossiliferous 

 here, as is the case with the oolites of the Lower Limestones. A 

 few large Gervillice and a stray CyTindrites were noted ; and there 

 are also undeterminable specimens of Nerinoea. 



The " Intermediate Series " (B, c) of our section is rather an arbi- 

 trary group, and one difficult to define. We take as its base the 

 lowest sheet of gritty shelly limestone which projects above the 

 softer white oolite in the " White Quarry." This lowest portion is, in 

 places, a blue-hearted stone with impure brashy partings of consider- 

 able thickness, and is petrologically distinct from the beds below. The 

 lower middle portion, which may be seen by dint of scrambling up 

 the steep slope above the quarry, is softer and more gritty ; whilst 

 the upper portion is more oolitic, being frequently conspicuous for 

 quantities of large Chemnitzia, as may be seen in the cutting in the 

 Seavegate-road, where the lowest beds visible belong to this group. 

 Here about 10-12 feet of buff hackly impure oolite and other lime- 

 stone is exposed. In assigning a thickness of 34 feet to the " Inter- 

 mediate Series," we consider it to terminate with the highest bed 

 beneath the oolite that we recognize as identified with the base of 

 Seamer Quarry (presently to be described). This estimate is, 

 perhaps, somewhat in excess. 



The whole series, however, is so highly calcareous, and so fre- 

 quently oolitic, that the upper line especially is hard to trace ; and 

 it may be asked why these beds should be separated from the lime- 

 stones above and below. The reason is, that here, and especially in 

 the lower middle portion, certain gritty appearances occur. On 

 this horizon, therefore, we must look for the representatives of the 

 vast mass of grit which further westward is seen to separate the 

 two limestone series. This grit will be referred to subsequently as 

 the Middle Calcareous Grit ; and where that distinction can be well 

 drawn, the calcareous equivalents of our " Intermediate Series " will 

 usually be referred to the Upper and Lower Limestones respectively. 



The Upper Oolite (6), or Coralline Oolite of Seamer. These beds 

 may be seen in a small quarry close to the top of Seavegate, on the 

 road from Ayton to Hackness (just above d in the word "road"). 

 Astarte Duboisiana and a few Rhabdophyllice may be noted. This 

 is seen to underlie the regular Thamnastrcea-Ra.g (a) of the district. 



The Coral Rag (a) has a thickness of 14-15 feet in the above 

 quarry, but appears to thin out, or to have been denuded off on the 

 rise. As the gravel (a?) slips over the side of the hill, its presence or 

 absence is more or less a matter of conjecture; but coral doggers 

 may be noted on both sides of Seavegate Gill. In the direction of 

 the dip the Rag maintains its full thickness through the village of 

 East Ayton, where it is quarried down to the level of the river. 



We have thus a total thickness of about 130 feet, made up of 



