TRANSACTIONS OF SECTION C. 633 



The following Papers and Reports were read : — 



1. Discovery of the Olenellus-zowe in the North-west Highlands. 

 By Sir Archibald Geikie, F.B.8., Director- Oeneral of the Geological Survey. 



Ever since tlie Geological Survey began the detailed investigation of the 

 structure of the North-west Highlands of Scotland the attention of its officers has 

 been continuously given to the detection of any fossil evidence that would more 

 clearly fix the geological horizons of the various sedimentary formations which 

 overlie the Lewisian gneiss. A large collection of organic remains has been made 

 from the Durness Limestone, but it has not yet yielded materials for a satisfactory 

 stratigraphical correlation. The study of this collection, however, has confirmed 

 and extended Salter's original sagacious inference that the fauna of the Durness 

 limestone shows a marked North American fades, though, according to our present 

 terminology, we place this fauna in the Cambrian rather than in the SOurian 

 system. Below the Durness Limestone lies the doloniitic and calcareous shaly 

 group known as the ' Fucoid beds/ which, though crowded with worm-castings, 

 has hitherto proved singularly devoid of other recognisable organic remains. In 

 following this group southwards through the Dundonnell Forest, in the west of 

 Eoss-shire, my colleague, Mr. John Home, found that, a few feet below where its 

 upper limit is marked by the persistent band of ' Serpulite grit,' it includes a zone 

 of blue or almost black shales. During a recent visit to him on his ground, when 

 he pointed out to me this remarkable zone, I was struck with the singularly 

 unaltered character of these shales, and agreed with him that, if fossils were to be 

 looked for anywhere among these aucient rocks, they should be found here, and 

 that the fossil-collector, Mr. ArtJiur Macconochie, should be directed to search the 

 locality with great care. The following week this exhaustive search was under- 

 taken, and Mr. Macconochie was soon rewarded by the discovery of a number of 

 fragmentary fossils, among which Mr. B. N. Peach, who was also stationed in the 

 district, recognised what appeared to him to be undoubtedly portions of Olenellus. 

 The importance of this discovery being obvious, the search was prosecuted 

 vigorously, until the fossiliferous band could not be followed further without 

 quarrying operations, which in that remote and sparsely inhabited region could not 

 be at that time undertaken. The specimens were at once forwarded to me, and 

 were placed in the hands of Messrs. Sbarman and Newton, Paleontologists of the 

 Geological Survey, who confirmed the reference to Olenellus. More recently 

 Mr. Peach and Mr. Home, in a renewed examination of the ground, have found, in 

 another thin seam of black shale interleaved in the 'Serpulite grit,' additional 

 pieces of Olenellus, including a fine head-shield with eyes complete. There may 

 be more than one species of this trilobite in these Ross-shire shales. The specific 

 determinations and descriptions will shortly be given by Mr. Peach. 



The detection of Olenellus among the rocks of the North-west Highlands, and 

 its association with the abundant Salterella of the ' Serpulite grit,' aft'ord valuable 

 materials for comparison with the oldest Paleozoic rocks of other regions, parti- 

 cularly of North America. The ' Fucoid beds ' and ' Serpulite grit ' which inter- 

 vene between the quartzite below and the Durness Limestone above are now 

 demonstrated to belong to the lowest part of the Cambrian system. The quartz- 

 ites are shown to form the arenaceous base of that system, while the Durness 

 Limestones may be Middle or Upper Cambrian. On the other hand, the Torridon 

 Sandstone, which Murchison placed in the Cambrian series, can now be proved to 

 be of still higher antiquity. The marked unconformability which intervenes 

 between it and the overlying quartzite points to a long interval having elapsed 

 between the deposition of the two discordant formations. The Torridon Sand- 

 stone must therefore be pre-Cambrian. Among the 8,000 or 10,000 feet of strata 

 in this group of sandstones and conglomerates, there occur, especially towards the 

 base and the top, bands of grey and dark shales, so little altered that they may be 

 confidently expected somewhere to yield recognisable fossils. Already my col- 

 leagues have detected traces of annelids and some more obscure remains of other 

 organisms in these strata. These, the oldest relics of life yet known in this country, 

 have excited a vivid desire in the Geological Survey to discover further and more 



