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



characteristic fossils — Ammonites biplex, Pecten midas, Avicula ova- 

 lis, var. obliqua, two species of Lucina, Thracia, Pleuromya, &c. 



No. 2. The Upper Coral Rag. There can be no doubt that this 

 is the true Coral Rag of Ayton &c. Only the harder portions, 

 the coral mineralized in situ, are visible; and these contain few 

 fossils other than Lithodomi ; an exposure of the intercoralline brash 

 would doubtless exhibit the usual fauna, already indicated. The 

 thickness is merely estimated. 



No. 3. The Upper Coralline oolite. This, too, is confined to a 

 limited area, and may best be studied in the Bell-heads quarry, where 

 we note the following section : — 



ft. in. 



a. Rubbly limestone fragments with occasional coral doggers in a red- 



dish soil ; abundance of Phasianella striata 1 



b. Large-grained oolites in a bluish grey calcareous paste. P. striata, 



Chemn itzia, Astarte Dvhoisiana, A. ovata, &c 7 



c. Strong band of Thecosmilia-VB.g — a kind of Coral shell-bed, show- 



ing a handsome arabesque of fossils. Spines of Cidaris Smithii, 

 in great abundance, quantities of Exogyra nana, Ostrea gregaria, 

 Nerincea, sp., Cerithium inornatum, Littorina muricata, Cylin- 

 drites Lhuidii, Area quadrisulcata, A. pectinata = 2 9 



d. Thick-bedded large-grained oolites, similar in character to those 



above, but rather softer ; beds visible 6 3 



17 



The general accordance of this section with what we have already 

 seen at Seamer leaves us no room to doubt that here we have the 

 representative of what is usually known as the Coralline oolite of 

 that locality. The band of Thecosmilia-xag in the oolite with so 

 many of the same fossils, the presence of Phasianella stnata and 

 Astarte Duboisiana in considerable numbers in the upper portion of 

 the oolite, all point in the same direction, and go to prove the identity 

 of this formation, making due allowance for variation, with that 

 which immediately underlies the great stretch of Coral Rag between 

 Seamer and Brompton. 



No. 4. The lower portions of the Bell-heads limestone pass, we 

 presume, into the gritty limestones called by Mr. Fox Strangways 

 the Middle Calcareous Grits. We have seen no good exposure of 

 these beds at the base of the upper oolite on LofFeyhead Heights, 

 unless certain gritty layers represent them ; but further back towards 

 Silpho they are more spread out and occupy a considerable extent 

 of ground. 



Nos. 5, 6, and 7. The great group of the Lower Limestones has 

 been far more extensively preserved on the Hackness outlier, as these 

 rocks may be seen on both sides of the many-fingered ravine, which 

 divides the heights of Silpho, comprising the limited region just men- 

 tioned, from those of Suffield. It has probably in most places, in- 

 cluding the Lower Coral Rag and passage-beds, a total thickness of 

 not less than 50 ft. Taking the Suffield district in this case as our 

 principal guide, we subjoin the following rough outline of their de- 

 velopment. 



No. 5. The Lower Oolitic Series. 



