THE CORALLIAtf EOCKS OF ENGLAND. 357 



passage-beds: they are well seen under the great elm tree on 

 Oswaldkirk bank, where they appear as buff ealc-grits with straw- 

 coloured ova, and are blue-centred in layers : there is a gradual 

 increase of calcareous matter upwards. Fauna scanty — a stray 

 Chemnitzia, Avicula ovalis, Opis Phillipsi, all small. Probable 

 thickness from 15 to 20 feet. 



Above these the Corallian Limestones are well developed. The 

 lowest bed, at the great elm tree, is a very white limestone with 

 sparry shells, mostly Chemnitzia. Commencing from the eastwards 

 we have a fine exposure in Oswaldkirk quarry, h of fig. 17. 



ft. 



5. Upper Calcareous Grit 8 



4'. Coral Rag 22 



4. Chemnitz ia-limestones (Coralline oolite) 24 



54 



The thickness of the Coralline oolite (4) in Oswaldkirk is from 

 25 to 30 feet. The difference between this class of rock and the 

 overlying Rag is not so marked within the range of this section. 

 The beds are mostly thick blocks of creamy limestones, with a few 

 buff-coloured ova, very much resembling in their lithological aspect 

 some of the intercoralline beds of the Hag ; but the absence of 

 Cidaris florigemma and of recognizable corals constitutes a difference 

 which becomes more marked as we descend. Chemnitzia hedding- 

 tonensis, Nerincea, Astarte ovata are the most usual fossils. The 

 lower beds yield Ammonites plicatilis. Following this subdivision 

 on the rise, we find it on the top of the hill at quarry / with only 

 6 feet of Rag over it. 



Section at Quarry f, on the top of Oswaldkirk Hagg, 



ft. in, 

 5. Irregular patches of Upper Calcareous Grit, associated with a fer- 

 ruginous clay filling hollows. 



4'. Coral Rag (see postea, page 358) 6 



4. Ckemnitzia-limestones,, the equivalents of the Coralline oolite, as 

 follows : — 

 a. Creamy limestones with a few univalves, alternating with 



brownish hackly oolite and brash 6 



)3. The principal shell-beds : Chemnitzia hed ding ton en sis of 

 all sizes in great profusion ; Nerincea, Astarte ovata, Exo- 

 gyra nana plentiful ; Lucina oculus, Littorina muricata, 



Cerithium muricatum less plentiful 6 



y. White creamy limestones with buff-coloured granules : few 



shells 9 21 



27 



This depth of 21 feet probably represents the full thickness of the 

 equivalent of the Coralline oolite, which has its last exposure in 

 Ampleforth-Beacon quarry. Westwards of that quarry it crops out, 

 or else thins out to a feather-edge ; we are not certain which is the 

 real fact. 



