Reports and Proceedings — Geological Society of London. 327 



rock-groups occur in the neighbourhood treated of: — (1) Gneisses 

 and crystalline schists more ancient than any of the others ; (2) the 

 Cassana Schiefer, a name applied to a variable group of rocks, 

 ranging from true schists to dark shaly rocks, apparently less 

 crystalline and more recent than the above-named, but older than 

 (3) the Verrucano, a conglomerate or grit with occasional mud- 

 stones, sometimes associated with a quartz-porphyry, the last 

 representing the well-known rock in the Botzen district ; (4) the 

 'Mittelbildung' of Theobald, strata intermediate between the 

 Verrucano and the Haupt-Dolomit, very variable in lithological 

 character, in which sometimes the Arlberg Kalk and Virgloria 

 Kalk can be identified, and typical rauchwacke, which occurs at 

 two levels. Above this comes (5) Haupt-Dolomit of the usual 

 character, followed in places by beds (6) of Rhgetic age. Of more 

 local occurrence are (i) serpentine, a large mountainous mass on 

 the western side of the Davoser See, with a narrow extension north- 

 ward and southward for a considerable distance; (ii) red and green 

 schistose rocks; (iii) radiolarian chert; (iv) breccias; (v) the so- 

 called talc-granite; and (vi) diabase, among which, at Arosa, is a 

 variolite. The schistose rucks (ii) are common in the neighbourhood 

 of the East Alpine serpentines, and in this region the latter rock 

 passes down on the western side into ophicalcites, which are 

 followed by a confused mass of layers of serpentine alternating 

 with reddish calcareous or argillaceous bands. These the author 

 considers to indicate a physical condition rather than a geological 

 horizon. With the red and green schistose rocks, which he refers 

 to the Mittelbildung, radiolarian cherts are associated. These have 

 been examined by Dr. G. J. Hinde, who states that the radiolaria 

 are not sufficiently well preserved for specific identification, but 

 have rather a Jurassic facies, though they also resemble radiolaria, 

 described by Professor Parona from Cesara, which that author 

 regards as at any rate not newer than Lower Trias. 



The author discusses at length the physical structure of the 

 district. The general ti-end of the Davos Valley is rather oblique 

 to that of the greater rock-masses, which, however, is somewhat 

 irregular. He shows that these (which have a general dip towards 

 the south and east) form three great acute and rudely parallel over- 

 folds, the westernmost being the most complicated ; of this fold the 

 serpentine forms a part. It is more recent than the crystalline 

 schists and the Casanna Schiefer, and is associated with the red and 

 green schistose rocks already mentioned, in a way which he 

 considers indicative of intrusion ; but it nowhere cuts the Haupt- 

 Dolomit. Accordingly he considers it to be later than the 

 Verrucano, and not earlier than the middle part of the Trias. 

 Certain crystalline breccias occur in the neighbourhood of the 

 serpentines ; these the author considers to be due to earth-movement, 

 and he goes on to give reasons for regarding them as the equivalent 

 of the Casanna Schiefer of other localities. There is, in his opinion, 

 no evidence of the presence of post-Jurassic strata such as Professor 

 Steinmann believes to exist. 



