THE CORALLIAN ROCKS OF ENGLAND. 289 



in infinite numbers, are Ostrea gregaria, Lima densepunctata, L. 

 pectiniformis ; and amidst the coral growth we find Littorina muri- 

 cata, Opis Phillipsi, Gastrochrena recondita, Pecten lens, P. suhtex- 

 torius, Exogyra nana, Cldaris Smlthli, Pseudodiadema versipora. 

 This reef, the absence of Cldaris florigemma from which is a most 

 noteworthy circumstance, is the only representative on this side of 

 Calne of all the beds elsewhere seen above the Lower Calcareous Grit ; 

 and in spite of the agreement of its coral fauna with that associated 

 with Cidans florigemma, its molluscs and echinoderms point, in our 

 opinion, to an early age, not far removed from that of the calcareous 

 grit on which it rests. We regard this therefore as an interesting 

 example of an earlier-formed reef than usual, such as we find, though 

 not commonly, in Yorkshire and elsewhere. 



In approaching Calne we come to the locality of the chief section 

 given by Lonsdale, which has been of great use to us, and which we 

 are able to confirm, though it seems to us that there is still some- 

 thing to be said about this neighbourhood. 



The sandy beds at the base, like those forming a modern sand- 

 bank, such as was here formed towards the close of the Oxfordian 

 period, thicken rapidly and as rapidly die away, so that in Bo wood 

 Park and to the north they occupy square miles of country, but six 

 miles from Calne they have become so thin as to be only recognizable 

 as a single bed. 



The characters of these beds where best developed in this district 

 may be studied in the railway-cutting, in a quarry near Conygre 

 Farm, and in another near the Bremhill and Studley road ; from 

 these combined we obtain the following 



Section of the Lower Calcareous Grit near Calne, in descending order. 



ft. in. 



1. Rubbly calcareous grit with numerous shell-fragments ; among 



them Ceromya minima, Pecten Jibrosus, Ostrea solitaria 2 



This is still more rubbly in the Conygre Quarry. 



2. Rock of similar structure, but more arenaceous, and running 



into bed s 1 3 



3. Loose sand 2 



4. Solid block of calcareous grit 1 



5. Loose sand 7 



The above description and thicknesses are derived from the 

 section in the railway-cutting ; but in the Conygre Quarry 

 they are more irregular and of smaller total thickness 

 (about 9 ft.). The hardened bands are irregular in their 

 position ; and the whole deposit, though not exactly false- 

 bedded, was evidently formed in disturbed or moving 

 waters. 



6. Solid block of blue-hearted calcareous grit of very compact 



structure, sometimes in two bands, and showing branched 

 fucoid forms on weathering 3 



7. Loose sand of a dark colour, and apparently graduating in the 



railway-cutting into true Oxford Clay ; but in the Bremhill- 

 road Quarry showing more beds of grit, which are very 

 variable, and with scarcely any fossils 9 



Q. J. G. S. No. 130. u 



