Vol. 55.] GEOLOGY OF THE DAVOS DISTRICT. 395 



types. ^ He is of opinion that the general facies is not unlike that 

 known from Alpine Jurassic rocks, but points out also that this 

 facies is similar to that of the radiolaria obtained by Parona ^ 

 from Cesana in rocks which, that observer believes, cannot be more 

 recent than Lower Trias, and may belong to the Permian.^ 



As Theobald has observed, there are similar siliceous ' inclusions 

 in the Liassic Algauschiefer and in Lower Jurassic strata on the 

 left side of the Rhine.' If there were thus a recurrence in Jurassic 

 times of conditions similar to those of the early Trias, there is 

 nothing improbable in the reappearance of a similar radiolarian 

 fauna. 



The stratigraphical evidence, as I hope to show later on, for the 

 pre-Triassic (or Lower Triassic) age of the Red Shales and Radio- 

 larian Cherts is very strong, and it is somewhat curious that this 

 view does not seem to have occurred to Theobald, who, in his 

 description, has given strong reasons in its favour.* Thus, in 

 describing the Yerrucano, he states that the upper layers become 

 ' shaly ' and pass into ' red Servino ' (the shaly type of Yerru- 

 cano), ' often with quartz - schists, red jasper and hornstein.' 

 Elsewhere, in describing his ' rothe Schiefer,' under the heading 

 of ' Biindner Schiefer ' (using that term, of course, in its old and 

 comprehensive sense), he again refers to the presence in them of 

 hornstone, quartz-schists, and jasper. Then he points out that 

 the red ' Biindner Schiefer ' cannot be distinguished from the 

 red Yerrucano (Servino), and notes the presence of similar red 

 layers in the Raibler and Liiner Schiefer (Lower Trias). The 

 latter fact has also been mentioned by Heim.^ In describing the 

 Yerrucano he states that ' in the upper strata, close beneath the 

 Secondary formations ... in the shaly argillaceous, mostly deep red 

 altered beds, limestone and dolomite-concretions come in, which 

 even join together to form thin bands of siliceous and argillaceous 

 limestone.' 



(v) The Breccias. 



Evidence of the breaking and crushing which many of the rocks 

 have undergone during the earth-movements which produced the 

 Alps may be found at several levels in the Rhaetic and other 

 strata ; but in addition to this local evidence of disturbance in 

 particular layers there are certain areas near Davos occupied by 

 distinct breccias of considerable thickness. I am unable to say 

 whether they are the same as those described by Steinmann, 



^ The genera represented are SphcBrozoum (spicules), CenoaphcBra, Cenellipsis, 

 Spongoprunum, Lithapium, Rhopalastrum, Archicapsa, Sethocapsa, Dictyo- 

 mitra, Ellipsoxiphus, Staurosphcera, Dicolocapsa, Lithomitra, Tricolocapsa (?), and 

 Theosyringium (?J. 



2 Parona, 'Sugli Schisti silicei a Radiolaria di Cesana presso il Monginevra,' 

 Atti R. Accad. Sci. Torino, vol. xxvii (1892) pp. 309 et seqq. 



' Parona & Rovereto, ' Diaspri Permiani a Radiolarie di Montenotte,' ibid. 

 vol. xxxi (1895) pp. 177 et seqq. 



* Theobald, Beitr. geol. Karte d. Schweiz, 2te Lief. 1864, Petrograph. Introd. 

 pp. 27, 33, 44. 



' Heim, ' Untersuchungen iiber den Mechanism us der Gebirgsbildung,' 1878, 

 p. 42. 



