. The Quarterly journal of the Geological Society of London . pper Oxfordian limestone. 4. Middle Oxfordian limestones or marls, 260 feet. 5. Lower Oxfordian ironstone, 33 feet. Equally important, however, in this case are the subdivisions ofM. Cotteau (34, 42), though they are not very definitely are as follows :— PORTLANDIAN. 1. Zone of Pinna suprajurensis. 2. Zone of Ammonites gigas. KlMMERIDGIAN. Sequanian. 1. White limestones. 2. Lithographic limestones. CoRALLIAN. Diceras-beds. Oxfordian. 1. Zone of Ammonites plicatilis and Cidaris fiorigemma. JURASSIC OF THE PARIS BASIN,
. The Quarterly journal of the Geological Society of London . pper Oxfordian limestone. 4. Middle Oxfordian limestones or marls, 260 feet. 5. Lower Oxfordian ironstone, 33 feet. Equally important, however, in this case are the subdivisions ofM. Cotteau (34, 42), though they are not very definitely are as follows :— PORTLANDIAN. 1. Zone of Pinna suprajurensis. 2. Zone of Ammonites gigas. KlMMERIDGIAN. Sequanian. 1. White limestones. 2. Lithographic limestones. CoRALLIAN. Diceras-beds. Oxfordian. 1. Zone of Ammonites plicatilis and Cidaris fiorigemma. JURASSIC OF THE PARIS BASIN, 531 The lower portion of the Oxfordian is not brought into this scheme,the last subdivision being in another scheme made the base of theCorallian. Two river-valleys cross this district, and the traverses made alongthese give a complete idea of the development of the rocks underconsideration, which here attain their maximum in the lower part,where they are truly marvellous. Fig. 9.—Map of the Valley of the Armandon, south of Tonnerre.(Scale 1 : 80,000.). We commence with the valley of the Armancon. At Ancy-le-Francan admirable section commencing in true Oxfordian rocks is seenabove the church. Towards the base are marly beds, with only an 2n2 532 J. E. BLAKE ON THE UPPER occasional calcareous band. The fossils at once indicate the horizon,those noted being Amm. tricristatus. A. Martelli, Pholadomya an-gustata, and Area rhomboiclalis ?. Traced upwards these marlsbecome more calcareous and are almost limestones. They are therecrowded with Pholadomya paucicosta, and have also , Cer-comya antica, Pinna lanceolata, a Trigonia like , and Pectendemissus. They become finally less fossiliferous, and are capped byshelly limestones. This series may be traced with the samecharacter westwards to a great roadside quarry, where a faceof 40 feet of sandy limestone is worked, and .so on to Pacy,where the well-known quarries have yielded many fossils, thechief of which a
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