JTTBASSIC OF THE PARIS BASIX. 



575 



On the coast of Calvados the sequence is tolerably plain ; for 

 the beds characterized by Cidaris florigemma succeed immedi- 

 ately to the Trouville Oolite, and thus occupy the base. They 

 change laterally into coral-growth, which represents the Coral 

 Rag; so that there is little, if any thing, that can be called " Coral- 

 line Oolite,"' unless it be the mass that underlies the Eag in the 

 Trouville quarry. The Supracoralline beds are here quite different 

 in form from those in the southern range, being arenaceous, instead 

 of calcareous or coralliferous ; nevertheless they contain calcareous 

 matter, and are admirably marked off stratigraphically from the 

 beds above by the difference of lithological character. The arena- 

 ceous character of these beds appears to prevent their assimilation 

 palseontologically with their calcareous representatives, the two sets 

 having little in common : nevertheless the fossils afford no nega- 

 tive to their stratigraphical correlation. In the well-known neigh- 

 bourhood of Glos, in like manner, can be traced the Coral Rag in 

 all its commonest characters, with perhaps a representative of a 

 Coralline Oolite below. Above, we appear to have a twofold de- 

 velopment of Supracoralline beds : — one, at the base, being calcareous 

 and similar to the Novion limestone and other southern supra- 

 coralline beds, wanting only the Diceras, but with abundance of 

 ramose corals ; the other, above, being an enormous development of 

 loose sand, corresponding to similar beds on the coast, and containing 

 a fauna which indicates a high position. These sands were placed 

 by Zittel and Gouert (under the guidance of Hebert) as Upper 

 Corallian, which corresponds to the above- assigned place. Their 

 relation to the coast-beds, and the correspondence of the latter to the 

 Sandsfoot-Castle beds of Weymouth, leave no doubt that the latter 

 must, with them, be placed as Supracoralline. We come thus to the 

 discussion of the Corallian of Dorset. There seems little doubt that, 

 the Sandsfoot-Castle beds being Supracoralline, and the Osmington 

 Oolite Upper Oxfordian, we must find the beds corresponding to the 

 Coral Rag between these limits. "What actually does intervene is 

 the Sandsfoot Clay and the Trigonia-beds. The abundant fossils of 

 the latter still leave some doubt as to its proper position. On the 

 one hand, such fossils as Gervillia aviculoides, Ammonites cordatv.s. 

 Pectenflbrosus, and EcJiinobrissus smtatus are extremely Oxfordian ; 

 while the presence of street eleltoieleet, Cidaris florigemma, and 

 Thanmastrcea aracJinoides attaches the rock to the Corallian. The 

 knot can only be cut by calling it a passage-bed, or by placing it 

 with other similar puzzles as " Coralline Oolite." It cannot, how- 

 ever, properly represent the true Coral Rag ; and thus we are driven 

 to look upon the Sandsfoot Clay as being its equivalent here, a cor- 

 relation not without value when other northern localities are con- 

 sidered. In jSorth Dorset the lower limit of the Corallian, as now 

 defined, is very well marked : for the uppermost Oxfordian is the 

 false-bedded series, and the overlying rubbly beds with Cidaris flori- 

 gemma cut off the upper edges. Nevertheless the palaeontology is not 

 altogether satisfactory ; and we are obliged to allow a wider range 

 than usual for more than one characteristic fossil, e. g. EcJiinobrissus 



