386 Proceedings of the Royal Physical Society. 



which, up to that time, had defied the attempts of geologists 

 to unravel. The results of this study appeared in his paper 

 before the Geological Society in 1882.^ By means of the 

 clue afforded by the Graptolites, he was able to show that his 

 " Barr Series " contained a Glenkiln (Upper Llandeilo) fauna, 

 his "Ardmillan" series a Hartfell (Caradoc) fauna, and his 

 " Newlauds " series a Birkhill (Llandovery and Tarrannon) 

 fauna. Viewed in the light of these facts, the apparent 

 anomalies presented by the study of other forms of life, 

 which had hitherto puzzled geologists, disappear, and the 

 fossils of the Girvan region arrange themselves along corre- 

 sponding lines to those which they do over the rest of 

 Britain and northern Europe. A confirmation of this state- 

 ment may be made by an appeal to the list of fossils from 

 the Silurian rocks of the Girvan area supplied by Mrs 

 Kobert Gray, a monumental list of fossils gathered, either 

 by her own hand or with the help of those of members of 

 her family.^ 



The publication of the paper on the Stockdale Shales of 

 the Lake District of England by Messrs Nicholson and 

 Marr, which appeared in 1888, has had a considerable 

 influence upon Scottish Silurian geology.^ In that paper 

 they apply the zonal method of mapping to the Tarrannon 

 rocks of the Lake District, which are there repre- 

 sented by a comparatively small thickness of pale shales, 

 but which they show to be capable of subdivision into 

 several life-zones, each characterised by forms of Graptolites. 

 Applying this knowledge to the Scottish rocks, the Geological 

 Survey found that over a wide area in the central and 

 southern parts of the Southern Uplands the grits and shales 

 contain identical forms of Graptolites to those of the Stock - 

 dale Shales, but distributed throughout a much greater 

 thickness of coarser strata. This fact is in accordance with 

 the evidence obtained throughout the whole of the Southern 

 Uplands, where, from the distribution of the sediments, the 



1 Q,uart. Jour. Geol. Soc, vol. xxxviii. p. 537, 1882. 

 '^ Me7n. Geol Sur., "The Silurian Rocks of Britain," vol. 1. pp. 686-697, 

 1899. 



■■■ Quart. Jour. Geol. Soc, vol. xliv. p. 654, 1888. 



