Cxlviii PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



of one great natural-history system. I need not follow further the 

 ingenious and successful effort of Sir Roderick to prove that the 

 system of classification which he was the first to originate in England 

 is equally applicable to every country in which the more ancient 

 palaeozoic deposits have been noticed ; and perhaps in nothing is the 

 truth of the proposition more manifest than in the position of the 

 Pentamerus-zones ; for, as Sir Roderick points out, the same species 

 of Pentamerus, Atrypa, &c. occur in two successive bands in England, 

 thus uniting together the faunas of the lower and upper Silurian. The 

 Pentamerus- zone in Esthonia is simply the central link of an un- 

 broken Silurian chain — the former being the result of accident or 

 physical disturbance, the latter the normal condition of the deposit. 

 It is, indeed, the object of Sir Roderick to prove that in Scandinavia, 

 as in Russia, Silurian rocks, both lower and upper, copiously charged 

 with characteristic fossils, form a united and unbroken whole, and, 

 viewed both palseontologically and geologically, exhibit a natural- 

 history system quite as complete and more easily understood than 

 their more expanded but much dislocated equivalents in the British 

 Isles. Species may indeed change, or undergo variations so great 

 as to be considered different ; but the grouping of the whole will 

 always enable the geologist to determine that he has arrived at a 

 Silurian deposit. 



The last paper of the official year was also by Sir Roderick Mur- 

 chison, and is directed to the elucidation of the succession of rocks 

 in the Northern Highlands. The object of this paper is to rectify both 

 the opinion which had been previously formed, that the mountain- 

 masses of red conglomerate and sandstone of the west coast of Scot- 

 land were detached portions of the Old Red Sandstone, and that of 

 Professor Nicol, that the quartzite and limestone occurring in this 

 series might be considered an equivalent of the Carboniferous series 

 of the South of Scotland. It will be observed that this latter opinion 

 was based on certain fossils found in the limestone of Durness by 

 Mr. C. Peach, and that Sir Roderick founds his alteration also upon 

 the fossils, after a determination of their true nature by Mr. Salter. 

 Sir Roderick first describes the fimdamental or true gneiss, which 

 is the basis of the whole series, then an accumulation of quartz- 

 rocks, crystalline limestones, chloritic and micaceous schists, and 

 younger gneiss. The fossils from the quartz-rocks consist of small 

 Annelide-tubes, now called Serpulites Maccullocliii, and traces of 

 fucoids ; they have been traced in beds for long distances by Mr. C. 

 Peach. The strong band of limestone between two quartz-rocks 

 contains, however, fossils of a higher degree of organization, namely, 

 a species of the genus Maclurea (M. Peachii, Salter) and its curious 

 twisted operculum, the genus being one formed by our American 

 friends ; again, Ophileta convpacta, a Canadian fossil, Oncoceras, and 

 a smooth species of Orthoceras with compressed siphuncle. They all 

 resemble Lower Silurian fossils of Forth America, which range from 

 the Calciferous rocks up to the Trenton limestone, but especially 

 grouped together in the limestones of the Ottawa River in Canada. 

 Following up the succession of rocks to the eastward, Sir Roderick 



