314 Geological Society : — 



some cases is amorphous and without any sign of bedding. "When 

 Mr. Tiddeman propounded his view that the limestone was 

 originally formed in the shape of knolls or mounds, the author 

 accepted his opinion for these particular hills. There is evidence 

 that the surface of limestone underneath the shales is uneven. 

 On Simon's Seat, a Millstone-Grit fell, there are swallow-holes 

 showing that limestone is not far below ; while below Thorpe 

 Fell at least 450 feet of shales overlie the limestone. The author 

 considers the absence of bedding in the limestone to be a very 

 important feature ; for in the country south of the North Craven 

 Fault, though the rock is excessively contorted, its bedding has not 

 been destroyed. 



3. ' On Three Species of Lamellibranchs from the Carboniferous 

 Eocks of Great Britain.' By Wheelton Hind, M.D., B.S., F.R.C.S., 

 F.G.S. 



May 10th.— W. Whitaker, B.A., F.R.S., President, 

 in the Chair. 



The following communications were read : — 



1. ' The Geology of the Davos District.' By A. Vaughan 

 Jennings, Esq., F.L.S., F.G.S. 



Alpine geology has attracted many workers since the date of 

 ■Prof. Theobald's classic memoir on the district of which Davos 

 forms part, and new principles of interpretation have been esta- 

 blished. The author has more especially studied (a) the age of 

 certain rocks formerly classed as " Biindner Schiefer," but distinct 

 from the grey shales variously regarded as of Jurassic or Ter- 

 tiary age ; (6) the origin and date of the serpentine near the 

 Davoser See ; and (c) the tectonic structure of the district. The 

 following rock-groups occur in the neighbourhood treated of: — 

 (1) Gneisses and crystalline schists more ancient than any of 

 the others ; (2) the Casanna 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 mudstones, 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-Doloniit, 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 llhsetic age. 

 Of more local occurrence are (i) serpentine, a large mountainous 

 mass on the western side of the Davoser See, with a narrow exten- 

 sion northward and southward for a considerable distance ; (ii) red 

 and green schistose rocks ; (iii) radiolarian chert ; (iv) breccias ; 



