406 STRATIGRAPHICAL GEOLOGY 



so that they are known as the " calcaire a, Gryphees," but they also 

 contain Coroniceras Bucklandi, Arnioceras bisulcatum, and other 

 fossils. These beds are from 100 to 130 feet thick, and are over- 

 lain by some 80 feet of unfossiliferous shales which occupy the 

 place of the higher zones. 



Charmouthian. In Alsace and Lorraine this stage consists 

 mainly of calcareous marls with ferruginous nodules, surmounted by 

 hard limestones with Paltopleuroceras spinatum, the whole being 

 about 200 feet thick. To the north-west in Luxemburg and the 

 Ardennes the lower beds become sandy, and near Mezieres the 

 succession, according to Professor Gosselet, is as follows : 



Feet. 



Ferruginous limestone with Paltopleuroceras spinatum . 130 

 Marls with Bel. clavatus and ^goceras capricornum . .160 

 Sandy limestone with Microceras planicostum ... 60 



350 



Toarcian. In Alsace and Lorraine this group consists in the 

 lower part of bituminous shales full of Posidonomya Bronni, but 

 also yielding Hildoceras bifrons and Harpoceras falciferum ; the 

 higher beds are marls with Lytoceras jurense from 10 to 12 feet 

 thick, while the shales below vary from 30 to 160 feet. 



The details of the Toarcian have been more fully worked 

 out in Normandy by Messrs. Braail and Buckman, 11 who have 

 recognised all the Dorset sub-zones, though the whole stage is only 

 32 feet thick and consists entirely of shales and clays. It is 

 directly overlain by limestone with Lioceras opalinum. 



In the district of the Jura Mountains the Liassic Series is not 

 so fully developed as the higher parts of the Jurassic System, but 

 the whole of it is exposed in different places and has the following 

 composition : 



Feet. 

 Toarcian. Marls and Posidonia shales . . . . . .150 



Charmouthian. Marls with Belemnites . . . . .100 



Sinemurian. Blue clays and Gfryphcea limestones ... 60 



Hettangian. Limestones ........ 6 



Rhcetic. Sandstones, marls, and limestones with a bone bed at the) ,. 

 base . j 



366 

 1. Germany 



The Lias is chiefly exposed in the south of Germany, its outcrop 

 extending in a long strip from the foot of the Black Forest on the 

 west through Swabia and then curving northwards by Nuremburg 

 to Bamburg, Coburg, and Baireuth. In this area it has been 



