JUKASSIC OF THE PARIS BASIN. 



577 



(41), Pellat was compelled to place them at least as Corallian, as he 

 identified the Coral Rag with that of Brucdale, and, at the same time, 

 noted that the overlying marls are on the horizon of the compact 

 limestone of Youecourt and of Tonnerre, both of which are Supra- 

 coralline. At a later date (56), owing to the supposed proof by 

 Sauvage (51) and Rigaux (53), that the equivalents of the marls of 

 the Mont des Boucards underlay, in the soundings, the Brucdale Coral 

 Rag, he met them halfway, and placed the two as equivalent. With 

 the breakdown of that proof is lost the necessity of disturbing the 

 former more correct reading, by which the coral-bearing beds of 

 Brucdale and the Mont des Boucards are the true Coral Rag, and the 

 marls of the latter place are Supracoralline, though not developed 

 at Brucdale. The occurrence, however, of Trigonia Bronnii in a 

 ferruginous bed above is too close a resemblance to the development 

 at Glos and Sandsfoot to allow us to place them in the Astartian ; 

 and we must raise the limit of the Supracoralline to, at least, the 

 top of this bed. 



The next division is the Kimmeridgian. Its limitation above 

 will be discussed later on ; as to its lower limit, a point much dis- 

 puted is, whether the beds called Astartian are to be included with 

 it, or with the lower beds. It is to this portion of the series, it 

 appears, that the term Sequanian was first applied by Mareou* ; and 

 it was considered part of the Kimmeridgian, while Thirria t had 

 previously called it Astartian. Neither of the original localities for 

 these names has, as yet, been examined ; but the latter is adopted 

 as most generally in use for a distinct portion of the series. De 

 Loriol (61) is probably the chief advocate for uniting the Astartian 

 with the Corallian under the term Sequanian, led thereto, perhaps, 

 by the supposed sequence in the Haute-Marne, and by his objection 

 to the term Corallian. It is, however, noteworthy that almost every 

 strati gr aphis t separates the Astartian from the Corallian, to associate 

 it with the Yirgulian or Pterocerian in one great group. It is so in 

 the description of the Ardennes (2), of the Meuse (13), and in Royer's 

 original description of the Haute-Marne (4). It is not so in Ley- 

 merie's description of the Aube (7), probably because he held all the 

 limestones at Clairvaux to be Astartian, nor in the same author's 

 description of the Yonne (25). But it is practically so in Cotteau's 

 description of the same (42), as the white limestone is made the 

 uppermost bed of his " Sequanian," which thus really is Supra- 

 coralline, and the true Astartian beds are left for the Kimmeridgian. 

 It is so in the Nievre (32), in the Cher (60), and in the Charente 

 (24) ; while in the Lower Charente, the coral-limestone being the 

 highest Corallian bed, it may be taken that the Astartian is not 

 specially recognized. On the coast of Normandy no one thinks of 

 associating the Trigonia-beds with the Coral Rag, or Supracoralline, 

 though they succeed the latter immediately ; and a study of the rocks 

 in the Boulogne area leads Pellat to the same conclusion (41). 



* Reckerches geologiques sur le Jura salinois, p. 116: 1846. 



t " Notice sur le terrain Jurassique," Mem. Soc. S. N. Strasbourg, 1830, p. 26. 



Q. J. G. S. No. 148. 2 q 



