294 
SILURIA. 
[Chap. XII. 
strata lie between the Lower and the Upper Coals, and may represent the English 
Millstone-grit. 
" 4. Upper Coals. — These occur in a thick series of sandstones, shales, fireclays, &c. like 
those of the Lower Coal Group. It is this upper series which forms the greater part of the 
coal-field of Ayrshire, and of that which stretches from Glasgow to Bathgate. It oc- 
cupies likewise the centre of the Mid-Lothian coal-field, and crosses the Firth of Forth 
into Fife. The fossils of this series of strata are chiefly Plants, with Shells of the 
genera Anthracosia, Myalina, &c, scales, spines, &c. of Rhizodus, Megalichthys, Ctena- 
canthus, &c, bones of Anthracosaurus &c. 
" Contemporaneous volcanic rocks have not yet been clearly detected in this group ; but 
in Ayrshire it is pierced with necks and bosses of felspathic trap and ash of Permian 
age ; and both in that county and in other districts it is cut through by dykes and 
masses of dolerite, which are, at least in part, of Tertiary age. 
" 5. Bed Sandstones and Marls. — These overlie the Upper Coals in Ayrshire, Lanark- 
shire, Fife, and Mid-Lothian. For the most part they are barren of organic remains, 
though in some of the argillaceous beds Carboniferous Plants occur, while in Ayrshire 
a seam of limestone near the top of the series contains Spirorbis carbonarius. In Ayr- 
shire these red sandstones sometimes rest directly upon the Carboniferous Limestone, so 
that they are not always conformable to the rest of the Carboniferous formation below. 
In the same county they are overlain by the Permian sandstones and volcanic rocks." 
Lower Carboniferous Rocks in Ireland. — In no portion of Europe, except 
Russia, are the Lower Carboniferous rocks more widely extended than in Ire- 
land, and at the same time so little productive of coal. This is doubtless in some 
measure due to the fact that by far the greater portion of the Irish series per- 
tains to the Lower Carboniferous division, which, though it is in Scotland, as 
above stated, very rich in coal and iron, exhibits no such qualities in those parts 
of England which lie in the same parallels of latitude as the mass of the Irish 
rocks of this age. Exclusive of the strata that are separated as being of Old 
Red or Devonian age (see p. 283), the ' Yellow Sandstone ' of Griflith, so defined 
where it is interstratified with limestone and shale containing Carboniferous fos- 
sils with Stigmatise, as in Scotland, is the oldest member of the system. This is 
followed upwards by schists, which assume a true slaty structure, particularly in 
the Cork district, and alternate with courses of limestone. The middle portion 
is composed of the great Lower Limestone, followed by the dark-grey earthy 
limestone known under the name of 1 Calp ; ' whilst the ' Upper Limestone ' of 
the midland and southern districts of Ireland is covered by the ' Millstone-grit ' 
with a little coal. 
Reposing conformably upon the Upper Red Sandstone described in the last 
Chapter (see general section at p. 281), this great succession of sandstone, lime- 
stone, and shale, the last occasionally affected by a slaty cleavage, is seldom, 
indeed, seen in one clear and consecutive section. Carboniferous Slates, forming 
the lowest part of the Irish series, are abundantly displayed on the coasts of the 
County of Cork, where their relations to the inferior and superior strata are 
very clear, and were long ago satisfactorily pointed out by Sir Richard Griffith, 
and have since been described in detail by Mr. Jukes. I have shown in the 
previous Chapter how these Carboniferous Slates overlie everything to which 
the term ' Devonian ' has been applied. The fossils of the slates are all truly 
Carboniferous, resembling those of the lowest Carboniferous zone near Barnstaple 
in Devonshire, and are clearly separable, as proved by Messrs. Salter and 
Etheridge, from the characteristic types of Upper Devonian age. It is, how- 
ever, to be noted that these Irish Carboniferous Slates so much resemble rocks of 
older age in their lithological conformation and oblique cleavage, that, but for the 
