^^1- 55'] GEOLOGr OP THE DAVOS DrSTKICT. 409 



nor are they evident on the Riiti slopes ; but above Monbiel aud 

 Klosters they are distinctly developed, together with crystalline 

 breccia and talc-granite, along the line mapped by Theobald as 

 Verrucano, and in close connexion with Verrucano of the more 

 usual conglomeratic type. 



The steep wall below the Cotschna ridge, and the spires of the 

 Casannaspitz, evidently belong to the same line of Hauptdolomit, 

 but there is a thinning in the centre, where the white bank of 

 gypsum, so plainly seen from Klosters, indicates the horizon of the 

 Rauchwacke. The band also thins out between the Casanna and 

 the Weissfluh, while on the east it narrows towards B,ied, but may 

 be found again as a thin line on the Eiiti slope and under the 

 serpentine of the Eastern Ehatikon. 



The Lithodendron-kaAk occurs in the detritus of the northern 

 slope, and its presence indicates that the calcareous part of the 

 Cotschna belongs to the series of crushed synclinal folds more plainly 

 represented elsewhere, though it is evident that the upper limb of 

 the fold is very different in constitution from that of the eastern 

 representatives. 



Turning next to the lower part of the northern aspect of the ridge, 

 with the view of ascertaining what strata reappear from below the 

 dolomite, one finds considerable difficulty in determining outcrops 

 with accuracy. The accumulation of talus- material is enormous, 

 and the detrital slopes are thickly wooded. Theobald has mapped 

 Verrucano, Casanna Schiefer, and ' gneiss,' as well as the ' red- 

 and-green schists,' as occurring below the dolomite, and there is no 

 doubt that the first three are represented by numerous blocks 

 scattered about the slopes. Under the Cotschna ridge itself, how- 

 ever, where one at last reaches the solid rock behind Hinter deni 

 Zug, one finds that the strata below the dolomite are the two 

 breccias already described. 



The upper breccia occurs as a bed severa-1 yards thick, composed, 

 as already stated, of angular fragments of limestone, dolomite, green 

 schist, and quartzite, all apparently embedded in a groundmass of 

 red Verrucano grit. The lower is the breccia of crystalline frag- 

 ments, with the black and ferruginous matrix and the semblance of 

 flow-structure, to which reference has also been made. 



What strata are present immediately below these breccias it is 

 difficult to say.^ A short distance to the east^ on the Klosters- 

 Davos road, the grey ' Bundner Schiefer ' seem to underlie the 

 attenuated dolomite directly, the breccias having locally dis- 

 appeared. 



Such being the nature of the rocks in immediate association with 



* It seems very probable that the serpentine, with or without red-and-green 

 Schiefer, is folded with the other rocks ; and it might be expected to reappear 

 near the overthrust-plane. I have not represented this in the section 

 (PI. XXVIl), as I have not observed it in the field. The serpentine-patches 

 mapped by Theobald west of the Weissduh and in the Arosa dietrict seem to 

 indicate, however, that such is the case. 



