JURASSIC OF THE PARIS BASIN. 



579 



both Buvignier in the Meuse, and Royer originally in the Haute- 

 Marne, included the lithographic limestones in the Astartian, 

 and Tombeck and Pellat do the same. It is therefore possible 

 that the line of junction ought to be carried farther down. In the 

 south of the Meuse the Yirgulian beds are well developed and very 

 fossiliferous ; but the lower portion has not yet been satisfactorily 

 marked off as Pterocerian, although from the recorded occurrence of 

 Pteroceras oceani at Mauvage, and the distinct grouping of the fossils 

 on the several horizons, such a subdivision might doubtless be made. 

 Tombeck has divided his Kimmeridgian into two zones, those of Amm. 

 orthocera and of Amm. caletanus, corresponding to the Pterocerian 

 and Yirgulian respectively ; and these subdivisions are accepted by 

 Pellat. In the Aube, contrary to the description of Leymerie, the 

 Astartian commences above the chalky limestone, and is characte- 

 rized throughout by rubbly and oolitic beds, with abundance of Tere- 

 bratula Leymerii. Near Bar-sur-Aube something of a Pterocerian 

 group may be made oat ; but the fossils have not been sufficiently 

 studied to draw a satisfactory line, which must be a palaeontclogical 

 one. In the valley of the Armancon we have the same difficulty 

 as in the Yonne to decide how far above the Diceras-beds the Astar- 

 tian must commence, the rubbly beds next above containing rolled 

 corals as well as Terehratula Leymerii ; but perhaps the line is best 

 drawn above the solid oolite block, as is done by Hebert (21) in 

 the neighbouring valley of the Yonne. No subdivisions correspond- 

 ing to the Pterocerian and Yirgulian have been made out in these 

 western districts. Plioladomya acuticosta is the most characteristic 

 fossil. As to the neighbourhood of Bourges, the chief feature is the 

 strong development of a Nerinsean oolite. The beds below this still 

 containing a species of Dicer as, seem certainly more referable to the 

 Supracoralline, in spite of their lying so far above the white lime- 

 stones certainly recognized as the latter ; and it might be a question 

 whether the Neringsan oolite ought not also to be placed below 

 the line of separation; but the presence of Plioladomya Protei, 

 Terehratula Leymerii, and Trigonia Baylii may be allowed to decide 

 it in favour of the consensus of opinion. In the Charente, the three 

 portions of the Kimmeridgian are recognizable, the Astartian com- 

 mencing where the beds become more marly and contain Oeromya 

 ecccentrica abundantly. This latter, however, is not a fossil which 

 can exclude beds from being Supracoralline ; and we may still re- 

 gard the line, therefore, as rather arbitrary. The upper two zones 

 are well distinguished palseontologically. The same may be said of 

 the Lower Charente : the Astartian may be commenced with the 

 marly beds of the Point d'Angoulins, with abundance of Terehra- 

 tula Leymerii, also Plioladomya Protei and Ceromya ecccentrica, the 

 latter certainly becoming locally characteristic ; and the Pterocerian 

 and Yirgulian are well distinguished, according to Hebert (54), at the 

 Point de Chatellailon. In Normandy, as at Weymouth, the Astar- 

 tian beds are better characterized than elsewhere. The change 

 from the calcareous grits of the Supracoralline is very marked ; and 

 the beds included in the zone, viz. theYillerville beds and the Trigo- 



2q2 



