^^^' 55'] TSE GEOLOGY or THE DAVOS DISTRICT. 389 



(y) The Partnach Schiefer are grey schists with calcareous 

 barjds, characterized elsewhere by special fossils. Theobald found 

 them distinct ou the Ehatikoii, and has marked them in the Ducan 

 basin and near Wiesen ; but I doubt whether they are generally 

 distinguishable. The ' Mittelbildungen ' on the Parsenn slope may 

 be in part referable to them. 



(^) The Virgloria-kalk (Schwarze Platten- or Tafel-kalk) 

 forms often a very distinct horizon, but here varies greatly. It 

 is a dark limestoue with tabular structure, and contains sometimes 

 siliceous or 'hornstone '-nodules. It is well developed and fossili- 

 ferous on the Rhatikon, and distinct in the Ducan and AViesen- 

 Amselfluh regions, but thins out or disappears in the Strela fold. 



(e) The Streifen Schiefer, below the Virgloria-kalk, have no 

 importance in the Davos area, though they have been mapped in 

 places. 



(() The Lower Rauchwacke is similar in character to the 

 Upper Kauchwacke, but often darker, less vesicular, and occasion- 

 ally siliceous. It frequently includes fragments of older rocks, 

 and tends to form a conglomerate passing into the Yerrucano.^ 

 It seems to occur in the Ducan and Wiesen-Amselfluh areas, but I 

 do not know of characteristic exposures nearer Davos. 



(iv) The Verrucano. 



Below the ' Mittelbildungen ' lies the problematic Yerrucano — 

 as constant in its presence as it is variable in character. The 

 typical red conglomerate, which has been variously referred to the 

 Carboniferous, the Permian, and the Trias, is well developed in the 

 neighbourhood of Wiesen and Glaris, and will be found in the form 

 of thin bands on each side of the other limestone-ridges. Where 

 the exposure is broadest, between the Korbshorn and the Amseltluh, 

 it forms the steep ridge so conspicuous from the eastern side of the 

 Davos Yalley, culminating in the conical peak of the Kummerhubel. 

 This, like the Sandhubel on the south, consists of a quartz-porphyry 

 or quartz-felsite such as farther east attains so great a development 

 in the vast sheets of porphyry that form the rich vineyard-country 

 of Meran and Bozen and the more eastern Tyrol. 



Although the map suggests that the igneous rock forms sharply- 

 marked intrusive patches, this is not really the case. The 

 conglomerate is often so full of felspars and corroded quartz- 

 crystals that it seems to pass into the ' porphyry,' and is a sort of 

 * quartz-porphyry -conglomerate ' such as that known in o;her 

 localities. 



In parts the conglomerate becomes very fine-grained, and passes 

 into a shaly sandstone. This, again, may become more argillaceous 

 and so pass into the red shales or the mottled red-and-green beds 

 that have been termed ' Servino.' Theobald also mentions the 

 presence of masses of jasper and hornstone in the Yerrucano (an 



^ This is Theobald's view. See also note on p. 394. 



