THE CORA.LLIAN ROCKS OJF ENGLAND. 



307 



In the first of these quarries (fig. 

 7) we have at the top about six leet 

 of magnificent Rag, the massive 

 portions growing in lenticular 

 masses with bases not horizontal, 

 and the intermediate spaces filled 

 to a large extent with Thecosmilice. 

 The reef-corals hero are in a 

 more perfect state of preserva- 

 tion than in any locality we 

 know of, and leave little to be 

 desired. Beneath the Rag is 

 the uppermost bed of the Lower 

 Calcareous Grit, a very remark- 

 able rock, composed of very sharp 

 fawn-coloured sand in a calca- 

 reous matrix, and containing 

 nodules surrounding Ammonites 

 cordatus, or enclosing a nest of 

 shells in which Gylindrites Luidii 

 is abundant. It also contains 

 Natica cli/tia, Gervillia avicu- 

 loides, Ostrea solitaria, and Serpula 

 tricarinata, and is the uppermost 

 fossiliferous zone of this portion 

 of the series. It is irregular 

 in the same quarry, and is pos- 

 sibly only a ^modification of the 

 sands below, as, where it thins 

 out and is only to be traced 

 just beneath the Coral Rag, the 

 sand contains similar nodules 

 here and there. The whole is 

 underlain by a strong bed of 

 Calcareous Grit, five feet in 

 thickness, with Natica marcha- 

 mensis, Cylindrites Luidii, and 

 Chemnitzia abbreviata, which cor- 

 responds to the Natica-bed at 

 Marcham. These beds probably 

 represent a later period than the 

 ordinary Lower Calcareous Grit, 

 approaching that of the Coralline 

 Oolite. 



In the quarry at the Cumnor 

 cross road we have an equally 

 remarkable development of the 

 Coral Rag, but with nothing like 

 the above-described beds under- 

 lying it. 



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