J. G. Goodchild — Deutozoic Rocks of North Britain. 593 



This upper subdivision is usually referred to as the Cornstone 

 Series. I have suggested in several papers that this chemically- 

 formed carbonate of lime of the Upper Old Red Cornstones marks 

 a transitional phase of climate. The land had sunk to near the 

 sea-level, and consequently humid conditions had set in, and 

 vegetation had begun to flourish. The decomposing remains of 

 trees, drifted into the lagoons, led to a precipitation of carbonate 

 of lime from the sulphate of lime held in solution by the concentrated 

 sea-water there. The presence of these cornstones is, therefore, 

 useful to the geologist as indicating transitional phases of climate 

 from arid to humid. Conversely, seeing that the same climatal 

 conditions must have prevailed over vpide areas, the occurrence of 

 cornstones at several localities within an area of limited extent 

 might safely be trusted as evidence of their contemporaneity. The 

 validity of this reasoning has lately been put to a very severe test, 

 which, I may add, it has successfully withstood. 



The fauna of the Upper Old Eed consists almost exclusively of 

 "fishes, which probably found their way into the sediments from 

 the rivers of upland origin, whose waters were dissipated by the 

 excessive evaporation when they reached the lowland areas. The 

 fish belong to species, and in some cases to genera, not found 

 elsewhere. Hence their remains serve a valuable purpose in 

 determining the age of the rocks in which they are found. Amongst 

 other fossil fishes may be mentioned such. Orossopterygians as 

 HolopUjchius and some of its allied genera ; the Ostracoderms 

 Asterolepis, Bothriolepis, and others ; such Dipnoans as Phanero- 

 jpleiiron, together with some other genera of equal biological interest, 

 but as zonal forms of lesser interest to the geologist. Dr. Traquair 

 has shown that the Upper Old Red contains two distinct fish faunas. 

 The lower zone is characteristically developed around Nairn, and 

 the higher is well seen near Elgin. 



It is not strictly correct to speak of the Upper Old Red Sandstone 

 graduating upwards into the Carboniferous Rocks ; and, for the 

 same reason, it is equally incorrect to describe this formation as 

 the "Carboniferous Basement Bed." There can be no doubt that the 

 Upper Old Red is quite a separate formation from the Carboniferous 

 System, and it has certainly nowhere been seen to alternate with 

 any rocks of undoubted Carboniferous age. In Central Fife there 

 is a very marked overlap of the middle of the Lower Carboniferous 

 Rocks on to the Upper Old Red Sandstone ; and evidence is not 

 wanting elsewhere of something like a true unconformity between 

 the two formations. 



As regards the base of the Upper Old Red Sandstone, it has long 

 been known that, throughout Britain, it lies with a more or less 

 violent discordance upon the rocks beneath. In Cumberland and 

 Westmoreland the aggregate thickness of the rocks between the 

 highest and the lowest horizons of the Protozoic rocks upon which 

 it lies amounts to more than seven miles, i.e. 13,000 feet of Silurian 

 Hocks, 12,000 feet of the Bala-Arenig volcanic rocks, and fully 

 12,000 of the Skiddaw Slates, to say nothing of other formations 



