566 Notices of Memoirs — Wm. Gimn — Geology of Arran. 



age, though no organic remains have been found in them, are closely 

 related to the rocks of Ballantrae in Ayrshire, and similar beds 

 occur in various places along the Highland border, where they have 

 been described by Messrs. Barrow and Clough. In the Isle of Arran 

 these rocks are intimately connected with the Highland schists. 



The Old Eed Sandstone of Arran has been found to comprise two 

 subdivisions, and in North Glen Sannox the upper division lies 

 un conformably on the lower. This formation is not confined to the 

 ground north of the String road, as generally supposed, but extends 

 in places three miles to the south of that road, being well developed 

 in the Clachan Glen, where it is much metamorphosed by intrusive 

 igneous rocks. No fossils have been found in the Old Eed Sandstone 

 of Arran except PsilopTiyton princeps, specimens of which have been 

 obtained from the lower division in Glen Shurig. 



The Carboniferous formation, fine sections of which occur on the 

 shore at Corrie and at Laggan, is now known to occupy but a small 

 portion of the area of the island. Near Brodick Castle and in Glen 

 Shurig its width of outcrop is not much more than 200 yards, and it 

 does not reach the western shore, being overlapped in the interior 

 by unconformable beds of New Eed Sandstone. Beds probably of 

 Coal-measure age with characteristic Upper Carboniferous fossils 

 have been recognized at Sliddery Water Head, Corrie, The Cock, 

 and in various other places, but these have no great thickness and 

 contain no seams of coal. They represent apparently the basement 

 beds of the Coal-measures. 



The stratified rocks of the southern part of the island, consisting 

 of red sandstones, conglomerates, and marls, have been proved to 

 repose unconformably on the Carboniferous formation, and in places 

 they contain derived pebbles with Carboniferous fossils. All the 

 evidence points to their being of Triassic age, and they may easily 

 be divided into two series, the lower of which probably represents 

 the Bunter Sandstone and the upper the Keuper marls. These 

 Triassic rocks occupy the whole of the coast from Corrie southwards, 

 around the south end of the island, and the west coast up to Machrie 

 Bay, where they appear to lie conformably on the Old Eed Sandstone. 

 They also form a small area in the north-eastern part of the island 

 near The Cock. 



That still more recent formations once existed in the island, 

 whence they have been removed by denudation, is proved by the 

 presence of fragments of EhEetic, Liassic, and Cretaceous rocks in 

 a large volcanic vent which is probably of Tertiary age. These 

 fragments occur on the western side of the island in the district of 

 Shisken, on the slopes of Ard Bheinn, and they have yielded a con- 

 siderable number of characteristic fossils which have been examined 

 and determined by Mr. E. T. Newton. 



Some of the most important of the discoveries are those connected 

 with the old volcanic rocks of the island. A series of interbedded 

 lavas and tuffs is found in North Glen Sannox associated with 

 the schists and cherts previously mentioned. Like them they are 

 probably of Arenig age, and closely related to similar rocks at 



