136 Reports & Proceedings — Geological Society of London. 



supposed to have been formed on the sea-floor during the deposition 

 of tfie sediment : in the case of the Paris Basin, at any rate, thermal 

 metamorphism is excluded. With these observations Mr. Daly com- 

 pares a remarkable dolomite in Alberta, probably of Pre-Cambrian 

 age. It consists chiefly of grains of carbonate of rhombohedral form, 

 but certain layers are heavily charged with clumps and interlocking 

 grains of glass-clear orthoclase, from 0*01 to 005 mm. in diameter, 

 and without good crystal form. The total amount of felspar is 

 estimated at 37 per cent of the rock. It is suggested that these 

 crystals were also developed during the deposition of the sediment at 

 the ordinary temperature. 



R. H. R. 



I. — Geological Societt ov London. 

 1. January 9, 1918. — Dr. Alfred Harker, F.R.S., President, in the 



Chair. 



The following communication was read : — 



"The Highest Silurian Rocks of the Clun Forest District 

 (Shropshire)." By Laurence Dudley Stamp, B.Sc, A.K.C.L. 

 (Communicated by Dr. A. H, Cox, F.G.S.) 



Clun Forest is a large district — extending on both sides of the 

 Welsh Border — in which Upper Silurian rocks crop out over a wide 

 area, interrupted by outliers of Old Red Sandstone. The district is 

 separated from the typical Silurian area of Ludlow, which lies some 

 15 miles away to the east, by the great line of disturbance that 

 passes through Church Stretton and Old Radnor. 



The classification adopted for the highest Silurian strata is as 

 follows : — 



Old Ked Sandstone 



Temeside Shales 



Temeside 

 Group. 



Upper 

 Ludlow 

 Group. 



Down ton Castle Sandstone 110 



Series. 



Ghojietes Beds- 



^Upper 

 Lower 



Rhyjichonella Beds . 



Aymestry / Dayia Shales . 

 Group. \ 



Lower Ludlow Shales 



Total . 



Thickness 

 in feet. 



Purplish-red sandstones. 

 . 350 Olive-green shales with bands 

 of micaceous green grit ; a 

 fragment-bed, with Euryp- 

 terid and plant remains, 

 forms the upper limit. 

 Yellow sandstones and tilestones, 

 with shales and Platyschisma 

 Limestones. 

 50 Green laminated flags and blue 

 flagstones. 

 . 300 Irregularly bedded calcareous 



flagstones. 

 . 300 Grey calcareous flags with 



massive blue flagstones. 

 ? 300 Striped laminated shales and 

 mudstones. 

 Dark-grey shales and indurated 

 mudstones. 



1410 



The distribution and characters of the beds are described. The 

 succession compares very closely with that in the Ludlow district 



