The Olenellus-Zone in the North-West Highlands, lol 



mammalian bones, land-shells only, and occasionally flint imple- 

 ments. On the coasts of Devon and Cornwall it is separated from 

 the Eaised Beaches by old sand-dunes. 



In South Wales the beach occurs below the mammaliferous cave- 

 deposits, whilst material corresponding to the ' Head ' seals up the 

 cave-mouths. The ossiferous breccias of the caves are therefore 

 intermediate in age between the beaches and the ' Head.' 



The origin of the boulders is discussed, and it is inferred that they 

 have been brought, not from the French coast, nor from a sub- 

 merged land, but from a north-easterly source by floating ice 

 through the Straits of Dover. The mollusca of the Raised Beaches, 

 of which a list of 64 is given, are closely related to forms living 

 in the neighbouring seas. 



These Raised Beaches are not of the age of the Higher Valley- 

 gravels ; but the evidence (especially that yielded by the Somme 

 Valley deposits) points rather to their connexion with the Lower 

 Valley-gravels, and therefore, with the exception of the Caves, they 

 represent the latest phase of the Glacial Period. 



2. "The Olenellus-Zone in the North-West Highlands." By 

 B. N. Peach, Esq., F.R.S.E., F.G.S., and J. Home, Esq., F.R.S.E., 

 F.G.S. 



In the stratigraphical portion of this paper brief descriptions are 

 given of certain sections in the Dundonnell Forest, from eight to ten 

 miles N.N.E. of Loch Maree, which have yielded fragments of 

 Olenellus. The organisms are embedded in dark blue shales 

 occurring near the top of the ' Fucoid Beds ' and towards the 

 base of the ' Serpulite Grit,' forming part of the belt of fossiliferous 

 strata stretching continuously from Loch Eriboll to Strome Ferry — 

 a distance of ninety miles. 



In the Dundonnell Forest the basal quartzites rest with a marked 

 unconformability on the Torridon Sandstone. There is an unbroken 

 sequence in certain sections from the base of the quartzites either 

 to the ' Serpulite Grit ' or to the lowest bands of the Durness Lime- 

 stone. At these horizons the strata are truncated by a powerful 

 thrust, which, at Loch Nid, brings forward a slice of Archaean rocks 

 with the Torridon Sandstone and basal quartzite. 



The strata from the base of the quartzites to the base of the 

 Durness Limestone, exposed in the Dundonnell Forest, are compared 

 with their prolongations to the north and south of that region, 

 from which it appears that there is a remarkable persistence of 

 the various subzones identified in Assynt and at Loch Eriboll. But 

 between Little Loch Broom and Loch Kishorn dark blue shales 

 near the top of the 'Fucoid Beds' have been observed at various 

 localities, evidently occupying the same horizon as the Olenellus- 

 shales in the Dundonnell Forest. 



The serpulites (Salterella) associated with the trilobites in the 

 * Serpulite Grit ' occur in the basal bands of the overlying lime- 



K2 



