Work by the author on the rocks of the Upper Ordovician and Lower Silurian in Central Wales has led to a comparison with deposits of similar horizons in other areas. Several points of interest have arisen out of the investigation and may be of value in delimiting the zones of the Upper Ordovician and also in indicating the best workable definition of the base for the Silurian.

Our knowledge of the geology of the district fringing the Grampians in Perthshire and Angus has been limited in the main to the published 1 inch maps of H.M. Geological Survey of Scotland (Sheets 48 and 56 in particular). A few papers in the Quarterly Journal of the Geological Society about the middle of the last century deal with certain exposures of special interest. The writer of the present contribution has conducted recently a detailed investigation of the area between Dunkeld and Fern, and an account of the solid geology has been published. The glacial geology presents no less interesting material or problems and, while the major portion of the results is being held over until further field-work is undertaken, one aspect, and over a limited area, will be considered here.

On Sheet 339 of the One Inch (New Series) Map of the Geological Survey there is marked at Woolley, within the metamorphic aureole of the Dartmoor granite, between Bovey Tracey and Lust-leigh, a patch of “Permian” rocks. Upon inquiry the Director of the Geological Survey, Sir John Flett, informed me that this was an error and should have been marked as “Felsite”. As the rock constituting the outcrop presents unusual features and is very different from an ordinary felsite I feel that a description of it should be placed on record. Moreover, it appears to be a good example of a rather uncommon rock type.