TRANSACTIONS OF THE SECTIONS. 89 



striae running from N.W. to S.E.*, parallel to the valley. Strath Bran, also in the 

 direction of the valley, or nearly W. and E. Braambury Hill near Brora, the white 

 siliceous sandstone of the oolite beautifully smoothed and marked with striae 

 running W. towards Loch Brora and Ben Horn. Large angular masses of the old 

 red conglomerate are still resting on the striated rocks. North coast of Sutherland, 

 near Betty Hill, striae from E.S.E. to W.N.W. West side of the Kyle of Durness, 

 white quartz-rock with horizontal striae running N.N.E. to S.S. W. West coast of 

 Sutherland Ridge above Kyle Skow, gneiss polished and striated ; direction of striae 

 E.S.E. to W.N.W. 



The most remarkable instance of the dependence of the direction of glacier striae 

 on local conditions is seen near the Sound of Skye. At the upper extremity of 

 Loch Keeshorn, close to the bridge, the striae, on the old red sandstone, have 

 a direction from N. to S. parallel to the valley. On the east of the Loch in the 

 valley, followed by the road to Jean Town, the rocks, generally talcose beds of the 

 quartz series, are beautifully marked by striae running W. by N., or nearly at right 

 angles to the former. On the ridge and on the top of the hills between Balmacarra 

 and Kyle Aiken ferry, the striae are again from S. by E. to W. by N. At the foot 

 of Keppoch Hill on Loch Duich, an overhanging cliff is very distinctly marked by 

 horizontal striae from S.E. to N.E in the direction of the lake. Taken in connexion 

 with the Coolin Hills in Skye, shown by Professor James Forbes to be another 

 centre of glacier striae, these facts show a convergence of ancient ice-streams towards 

 the Sound of Skye. 



2nd. The second form of ice-action are transported boulders. Blocks of a very 

 peculiar granite were traced from the valley of the Alness above Ardross Castle, 

 where they are sometimes arranged as it were in moraines, over the whole promon- 

 tory of the Black Isle to the shores of the Moray Firth. Striated stones were seen 

 in the detritus near Cape Wrath. On the west coast of Sutherland, near Loch 

 Laxford, enormous blocks are often perched on the top of rounded bosses, or on the 

 very verge of precipices, like lines of sentries on the watch. As the slightest impulse 

 seems sufficient to dislodge these boulders, the manner in which they have been 

 placed in their present position is very problematicaL 



3rd. The third form of ice-action was observed on the coast of Caithness, near 

 the old castle of Wick. The top of the cliff, far above high water for nearly a 

 quarter of a mile, is covered by angular blocks, broken from the rocks below and 

 forced up, in a sloping position one over the other, like shoals of ice on the banks 

 of a river when breaking up after frost. The author ascribes this remarkable accu- 

 mulation to an iceberg grounding on the shore, and, from the position of the 

 fragments, considers that it must have been moving from the E.N.E. or E. 



On the Pterygotus and Plerygotus Beds of Great Britain. By D. Page. 



Without attempting to define with precision the vertical range of the Pterygotus 

 and other associated Crustacea, the author was of opinion that the zone of the 

 " Tilestones," — partly on the verge of Siluria and partly on the verge of Devonia — 

 might, with no great impropriety, be designated the " Pterygotus beds of Great 

 Britain." At all events, in this zone alone had the remains of Pterygotus and other 

 allied Crustacea been found most abundantly ; so abundantly, indeed, that these 

 creatures might be regarded as the characteristic fauna of the period. During the 

 last summer, he had examined pretty minutely the relations of the strata in Forfar, 

 Perth, Stirling, Dunbarton and Lanarkshire, and everywhere he had found them 

 maintaining the same stratigraphical position, and characterized by the same fossil 

 fauna. Co-ordinating them in like manner with the Ludlow and Hereford beds 

 (which had yielded fragments of Pterygotus, Onchus, Plectrodus, &c.), they appeared 

 to be on the same horizon ; and thus it was, he wished to group the whole of these 

 "Tilestone" strata as the " Pterygotus beds of Great Britain." The subject he 

 intended to lay before the Section naturally resolved itself into two divisions ; first, 

 what we know of the Pterygotus and its crustacean congeners ; and, second, the 

 range and limit of the scrata in which these crustaceans had been discovered. The 



* The directions are true, or corrected for the variation. 



