

1858.] MURCHISON — NORTHERN HIGHLANDS. 503 



The " Lower Silurian rocks, in the form of quartz-rock, crystal- 

 line limestone, chloritic and micaceous schists, and younger gneiss," 

 "were then described. The fossils from the quartz-rock consist of 

 small annelide-tubes, now named Serpulites Maccullochii, and traces 

 of fucoids. These fossils were long ago noticed, but of late they have 

 been traced in beds for great distances by Mr. Peach. The strong 

 band of limestone between two quartz-rocks is estimated by Colonel 

 James to lie about 800 feet above the base of the series, and is of 

 great extent. The fossils * detected in it have been determined by 

 Mr. Salter to be Maclurea Peachii, spec. nov. (and its curious twisted 

 operculum), Ophileta com.pacta, well known in Canada, Oncoceras, 

 spec, and Orthoceras, a smooth species with a compressed siphuncle. 

 They all closely resemble fossils of the Lower Silurian rocks of North 

 America, which range from the Calciferous rock up to the Trenton 

 Limestone, both inclusive, — a group especially to be found in the 

 limestones of the Ottawa River in Canada. 



Passing across Ross-shire in a more southern parallel, from Loch 

 Duich in Kintail, on the west, to the frontier of the Old Red 

 Sandstone on the east, the general succession of rocks was de- 

 scribed to be much the same as that in North-west Sutherland, 

 though there are considerable changes of lithological character when 

 the same rocks are followed southwards or south-south-west upon 

 their strike ; and the author stated his belief, that not only may the 

 regularly bedded limestones which are intercalated in the chloritic 

 and quartzose rocks of Dumbartonshire be classed with some of the 

 oldest of those stratified masses which, like the limestones of Suther- 

 land, are unquestionably of Lower Silnrian age, but that the vast and 

 evidently overlying masses of mica-schist and quartzose-gneissic flag- 

 rocks of the Breadalbane district may be some day found to be simply 

 the prolongations of the micaceous flagstones of the North-western 

 Highlands above alluded to, as overlying the quartz-rock and fossili- 

 ferous limestone : further, that in the still higher limestones and 

 schists seen on the banks of Loch Tay, we may speculate on the 

 existence of the equivalents of younger and higher strata than any 

 which are observed in the Northern Counties. 



After some observations on the truly stratified condition of these 

 micaceous and gneissose schists (younger gneiss) of the Highlands, 

 Sir Roderick proceeded to the consideration of the " Old Red Sand- 

 stone of the North-east of Scotland," — defining the tripartite division 

 of this great series, and demonstrating that the beds with Cephalaspis 

 Lyellii and Pterygotus Anglic us of Forfarshire really lie at the base 

 of the series, and are certainly of greater antiquity than the bitumi- 

 nous fossil-bearing schists of Caithness. This division is in accord- 

 ance with the relations of the deposits of the Devonian period, as 

 seen in Devonshire and Germany, though the lowest member of the 

 Old Red of Scotland has no representative in the Devonian rocks of 

 Russia. The Caithness flagstones were described as being in the 

 middle of the series ; whilst the underlying conglomerates and sand- 



* Twenty-three in all, 11 of which are identical with American forms. — 

 Oct. 1858. 



