
TRANSACTIONS OF THE SECTIONS. 49 
the same fossils; Prof. Sedgwick at Moffat also obtained Graptolites; and Sir Rode- 
tick Murchison, in the last year’s volume of the Journal of the Geologicai Society, 
has given an elaborate account of the Silurians of the south-west of Ayrshire and their 
fossil contents. These Silurians, described by Sir R. Murchison, occupy a higher 
position than those which constitute the great Silurian mass traversing the South of 
Scotland from sea to sea. 
In Ayrshire a deposit of limestone makes its appearance, which, both in lithological 
characters, and also in its fossil contents, shows an affinity to the limestone of Wrae, 
and above this limestone several deposits containing large quantities of fossils occur. 
The nature of the fossil contents of this limestone and that of Wrae indicate that they 
appertain to the Llandeilo flags. At Wrae this limestone is seen lying upon a breccia 
composed of fragments of slate, and at the same locality thick beds of the slate, from 
whence these fragments have been obtained, are also seen. ‘This slate extends east- 
north-eastwards and west-south-westwards, and is seen at Stobo in Peeblesshire, and in 
the summit-cutting of the Caledonian railway, where it shows great thickness. From 
thence it extends westwards through Lanarkshire and the north-east of Dumfries- 
shire to Cairn Ryan in Wigtonshire; and in this black slate Mr. Carrick Moore found 
Graptolites and other fossils. To the south of the zone occupied by these black slates, 
beds of greywacke, sandstones and shales are found, having great thickness; and 
beneath these a band of gray slate is met with. In this gray slate are seen, in some 
localities, the graptolites described by Prof. Nicol, and this gray slate band runs nearly 
parallel with the black zone. Besides Graptolites, it affords annelid markings and 
fucoids, both of which are found in considerable abundance at Barlae quarry in Kirk- 
cudbright. Southward of this gray slate the graywacke sandstones and shales again 
make their appearance, and in them there occurs a deposit of green and blue shales, 
which also contain annelid markings. Beneath these green and blue shales, after a 
considerable thickness of graywacke sandstone is passed through, beds of soft black 
shale are seen having abundance of Graptolites, of various species, and this grap- 
tolite-shale passes into anthracitic shale, in some localities consisting altogether of 
the latter mineral. Under the anthracite, graywacke sandstones and shales are 
again seen, and these appear to form the lowest beds of the lower Silurians, as they 
occur in the South of Scotland. In these low shales evidence of animal life is seen in 
the form of annelid impressions, and these are probably the lowest traces which have 
yet been obtained of animal existences. The lower beds of greywacke sandstones and 
shales, the anthracite band, and the accompanying graptolite beds, as well as some of 
the deposits which succeed them, are repeated three times in that portion of the area 
occupied by the Silurians, where they are best developed, viz. in Dumfriesshire. 
The gray shale, and the beds which succeed it, together with the higher black slates 
and breccia, do not appear to be repeated like the deposits which occur beneath 
them, consequently the order of sequence of the deposits in these lower Silurians is 
somewhat disturbed. However, between the Beatock station of the Caledonian rail-. 
way and Elvanfoot a comparatively perfect sequence may be made out, by examining 
the sections on the line of railway and the brook courses which fall into the Evan, 
the stream which runs parallel to the Caledonian railway. At Ruttenside near 
Greskin, about four miles above the Beatock station, the anthracite is seen in the 
Evan water, and this can be traced E.N.E. to Hartfell, and from thence into Peebles- 
shire and Selkirkshire. North from Ruttenside the greywacke sandstones and shales, 
which lie above the anthracite, make their appearance; and at Rae-cleugh, near the 
dine which separates Dumfriesshire from Lanarkshire, the gray slates were seen, 
which contain the Graptolites at Greistone, and the annelid markings and fucoids at 
Barlae. Following the railway northwards from Rae-cleugh, we come upon the 
greywacke sandstones and shales, which separate the gray slates from the black 
slates which occur above them; and these at the summit-cutting are succeeded by the 
black slates, which at Cairn Ryan afford Graptolites and other fossils. The hills of 
Crawford in Lanarkshire, which rise to the north of the black slate band, are com- 
posed of the breccia already alluded to; but the thickness of this breccia cannot be 
made out here, nor is it seen to be succeeded by the limestone containing Llandeilo 
flag fossils, as at Wrae in Peeblesshire. This section on the Caledonian railway is 
more than six miles long, and from the great inclination of the beds, which are rarely 
less than 70° N.N.W., it would seem to afford a series of deposits about 25,000 feet 
in — and by taking the conglomerate which lies below the limestone, and the 
52. 4 
