JTTEASSIC OF THE PAEIS BASIN. 



581 



beds ; and its complete fauna, as given by de Loriol, shows that 

 17 species are common to lower beds and only 10 to higher. Much 

 therefore might be said for making this Supracoralline ; but as there 

 is not much certainty about it, and it has hitherto been placed in the 

 Astartian, it may be left there, with the similar rock at Bourges, for 

 the present. Perhaps it would be preferable to draw the line im- 

 mediately above this, and include the F 2 F 3 of Pellat with the Gres 

 de Wirvigne. The fossils of the latter approximate closely to the 

 Astartian at Havre. The remainder of the Kimmeridgian is well 

 characterized here ; the lower portion, being apparently barren of 

 Pteroceras, would be better named after its Ammonite ; but the 

 upper part is markedly Yirgulian, and corresponds to the mass of 

 the " Lower " Kimmeridge Clay (so-called) of Dorset. In the Pays- 

 de-Bray only this portion is seen. 



For the series of deposits which overlie the true Kimmeridgian or 

 Yirgulian, and underlie the true Portland beds, the name of Bolonian 

 is proposed. It has already been proved* that in the Boulogne 

 area these rocks correspond to what had been hitherto considered 

 an integral portion of the Kimmeridge Clay ; and Waagen (35), by 

 separating them as a zone above the Yirgulian, came to practically 

 the same conclusion. For the lower portion of them, therefore, which 

 especially differs in lithological character from Kimmeridge Clay, and 

 is of the nature of an episode in its midst, the name of " Bolognian 

 episode " was formerly proposed. A further study of the same series 

 in the basin of Paris shows that elsewhere they are not specially epi- 

 sodal in character, but nevertheless require separation from the Yirgu- 

 lian. The name Portlandian has usually been applied to them ; but 

 since it is certain that they do not correspond to our Portland rocks, 

 but to beds below them, this name is to the last degree mislead- 

 ing f ; and the only way out of the confusion is the use of a distinct 

 name. Saemann is said by Pellat (39) to have proposed the name 

 Pontidian ; but as this is rejected by the latter, who alone mentions 

 it, it cannot be said to have priority ; and it is not a good geogra- 

 phical name. It seems therefore best to modify the name already 

 applied, and extend it to all the continental beds which, not being so, 

 have been called Portlandian. Some name connected with the term 

 " Calcaire du Barrois would have been better, if some true Port- 

 land stone had not been included in that term. 



These Bolonian beds admit of a twofold subdivision in almost every 

 locality, though the apparently natural limits in the several places may 

 not quite coincide. In the Boulogne area the two parts here distin- 

 guished have been called "Lower and Middle Portland." According 

 to Pellat, the fauna of the Lower Bolonian commences in the clays 

 beloiv the great conglomerates ; hence the change of fauna was not 

 brought about by the changes of physical character, but had already 

 commenced. The palseontological line will therefore not coincide with 

 the lithological one ; but the upper parts of the clay series are inde- 



* Quart. Journ. GTeol. Soc. vol. xxxvi. p. 189. 



t Some Swiss geologists hare been led by this misnomer to declare that there 

 are no Portland beds (in their sense) in the Isle of Portland ! 



