148 M. Studer on the Geohgical Structure of the Alps, 



they contain fuci, which seem. identical with F, intricatus 

 Brongn. ; also belemnites, which it has not yet been possible 

 to identify ; and rings of pentacrinites. The belemnites are 

 pretty frequent in the slates of the Nuffenen. M. Lardy pos- 

 sesses an ammonite from the slates of Salvent, which is be- 

 tween the group of Mont Blanc and that of the Aiginlles 

 Tiovges ; and the same species occurs in the middle or coralline 

 jura strata. Impressions of ferns, which cannot be distin- 

 guished from those of the coal, have been met with in slate?; 

 and sandstones on the western side of the Dent de Mercies, 

 on the Col de JBalme, in the Tarentaise, and in Dauphiny ; and 

 at several places in these districts beds of anthracite are regu- 

 larly mined. 



When the central mountain masses or groups are far 

 apart, as, for example, is the case in the Grisons and Valais, 

 the flysch acquires an extraordinary development, and itself 

 forms high chains and large mountain masses. It is sub- 

 jected at the same time to marked transformations, which 

 seem to bo intimately connected with the appearance of the 

 serpentines, and which in many cases render the mineralo- 

 gical determination of the rock a matter of great difficulty. 

 The colour of the slates and of the sandstones passes into 

 green; talc and chlorite make their appearance ; the mass 

 gradually passes into talc or chlorite slate ; the stratification 

 disappears, and diorites and spilites present themselves, most 

 frequently without its being possible to trace a limit between 

 the green slates, the aphanistic rocks, the serpentine, and the 

 gabbro ; and nevertheless we can easily assure ourselves on 

 the road of St Bernard, in the valley of Bagnes, and in most 

 of the southern valleys of the Valais, as well as in Oberhalb- 

 stein in the Grisons, that thes green slates, so extensively 

 distributed, cannot be separated from the ordinary grey flysch. 

 It is to this formation of green slates that ihepierres ollaires 

 belong, which are quarried at so many points in the Valais 

 and in the Grisons. 



When the central masses are very close to one another, as 

 is the case with those of the Finsteraarhorn and the St Go- 

 thard, the flysch is reduced to a narrow zone, and even disap- 

 pears entirely, oi- at least Is only represented by some detached 



