574 



J. F. BLAKE ON THE UPPER 



lithographic limestones, which are very different from the limestones 

 of Pacy. In fact, the limestones of Angy and Tonnerre are shown 

 to be the Supracoralline beds, and do themselves contain Diceras-beds, 

 especially at the top, though the whole is enormously developed, so as 

 easily to mislead one. On passing westwards, however, to the valley 

 of the Yonne, still more is in store ; for while in the neighbourhood 

 of Bailly and Yincelles the Supracoralline beds occur in all their 

 characters, beneath them are still found the lithographic limestones, 

 more than usually marly at Vermanton ; and below these again the 

 coral-beds of the Laignes valley, so much reduced in the Armancon, 

 burst out into a magnificent mass, wherein corals of all kinds, 

 Dicer as, Nerincea, and all the Rag fauna are confusedly mixed in ex- 

 treme abundance, as may be seen so well at Merry-sur- Yonne, 

 Chatel-Ceusoir, and, in a more uniform character, in the white lime- 

 stones of Coulanges. It is this development that for ever negatives 

 the idea that Diceras-beds are necessarily above the Coral Rag, though 

 these Dicerata differ from those of the Diceras-beds in apparently 

 having lived near the spot, and in not having been rolled. Beyond this 

 valley the Corallian once more changes, and by degrees returns to the 

 dead uniformity of a lithographic limestone. In the valley of the 

 Loire the lower Diceras-bed is seen in diminished thickness near La 

 Charite, succeeded in an upward direction by compact limestones, 

 which show no more character than that of becoming oolitic near 

 Pouilly. On the left bank of the river, however, it is stated (32, 60) 

 that the Lower or Coral-Rag Diceras-beds are not to be found, but that 

 the Supracoralline ones are once more developed at Sancerre. These 

 last take up again their Armancon form near Bourges, and show, not 

 quite at the summit, the white limestones of Angy and Tonnerre. 

 Hence to the Cher is the path of degradation ; for in the latter valley 

 even less can be distinguished than in that of the Aube, but all is 

 lithographic. In the Charente department the Corallian rocks remain 

 still massive and but slightly characterized, though coral-beds are 

 developed in what may be considered the equivalent of the Coral Rag. 

 The Supracoralline beds are still characterized by the abundance of 

 Nerincece and by the presence of Diceras and Cardium corallinum. 

 In the Lower Charente, on the shores of the Pertuis d'Antioch, the 

 Corallian rocks put on a fresh form, the lower part being a white f os- 

 siliferous limestone, which, by its fossils, may represent the Rag ; 

 while the true coral-bearing beds are on a horizon usually " supra- 

 coralline," and are parallel with the similar development in the 

 Ardennes. It would appear that d'Orbigny included still higher beds 

 in his ' Etage Corallien ' here ; but a comparison of the series in the 

 two Charentes and the general fauna indicate the necessity of draw- 

 ing the line separating the Corallian from the Astartian almost 

 immediately above the coral-reef of the Point du Che. In the 

 departments of the Orne and Sarthe, according to Hebert's descrip- 

 tion, there would appear to be no development of corals on the usual 

 horizon ; but the Supracoralline beds contain Diceras and are over- 

 lain by coral-growth, which is thus on a higher horizon than almost 

 anywhere else. 



