388 Proceedings of the Royal Physical Society. 



from which a Glenkiln (Upper Llandeilo) suite of Grap- 

 tolites was obtained by the Geological Survey. ^ North 

 of the Stinchar, the Kirkland and Benan conglomerates, 

 with the Stinchar limestone and Graptolitic mud-stones, 

 lie unconformably on the denuded edges of the Kadio- 

 larian Cherts and the Ballantrae igneous rocks, and the 

 conglomerates are made up of the well-rounded fragments of 

 the rocks of both these zones. The Graptolitic mud-stones 

 which are associated with the limestone, as shown by 

 Lapworth, contain several forms of Graptolite belonging to 

 the uppermost Glenkiln zone.^ The Ballantrae rocks of 

 this region were therefore raised from the bed of a clear 

 sea, converted into a land surface, which was deeply 

 eroded, and which supplied sedimentary material for a great 

 thickness of rocks during the life of the Glenkiln fauna of 

 Graptolites, or, in other words, during the Upper Llandeilo 

 period, while continuous deposition proceeded at a short 

 distance to the southwards.^ This unconformability prob- 

 ably marks the southern line of the area of disturbance at 

 the period when the Ballantrae rocks of the Highland border 

 were involved along with the Highland schists. 



The study of Palaeontology has contributed greatly towards 

 the correlation of separate areas occupied by Old Eed Sand- 

 stone strata in Scotland during the period under considera- 

 tion. Thus, the outlying volcanic and sedimentary rocks of 

 Lome have been proved to be of Lower Old Eed Sandstone 

 age by their containing a species of Oephalaspis, determined 

 by Dr Traquair to be nearly allied to C. Lyelli, as well as other 

 forms of life, like those found in Forfarshire, such as Ptery- 

 gotus anglicus, Kampecaris, and Parka decipiens. The dis- 

 covery of these fossils was made in 1897 by Mr Macconochie, 

 under the superintendence of Mr Symes, while carrying on 

 the Geological Survey of Argyleshire.^ In the same strata, 



1 Mem. Geol. Sur., "The Silurian Rocks of Britain," pp. 422, 429, 1900. 



^ Quart. Jour. Oeol. Soc, "The Girvan Succession," pp. 555-593, 1882; 

 Mem. Gkol. Sur., "The Silurian Rocks of Britain," pp. 487, 488, 1900. 



3 Mem. Geol. Sur., "The Silurian Rocks of Britain," p. 484, 1890. 



^Nature, vol. Ivi. pp. 157, 158, 1897; Mem. Oeol. Sur., "Simmary of 

 Progress for 1897," p. 82, 1898. 



