DESCRIPTIVE REMARKS, lxv 
In the North of England the limestone is much divided by beds of 
grit or sandstone, clays and shales ; in Yorkshire the Upper Limestone 
shale, and top of the Carboniferous Limestone, has been named by the 
late Professor John Phillips, the Yoredale series, and the thick Lime- 
stone below the Scar limestone. 
In some of the Coal districts which are within or contiguous to the 
Silurian formation, as at Dudley and Wolverhampton, the lower and 
central portions of the series, the Carboniferous Limestone and Mill- 
stone Grit are absent, the upper productive Coal Measures resting di- 
rectly on Silurian rocks. 
The Carboniferous formation in Scotland is well exhibited along 
the great midland valley, from the shores of the Clyde to the mouth of 
the Frith of Forth. The lower part of the system, as before alluded 
to, instead of the usual thick mass of limestone, consists for the most 
part of sandstones and shales, with comparatively few and thin lime- 
stone bands. 
In Ireland the lower portion only of this formation is extensively 
developed. The Carboniferous slate and Coomhola grits, forming its base 
in the county of Cork, has a maximum thickness of at least 5,000 ft. 
The Carboniferous Limestone of the South is of great thickness, usually 
forming low and gently undulating ground; it is covered by the Lower 
Coal Measures, consisting of black shales and grits, containing at their 
upper portion thin beds of Coal. The limestone spreads over a great 
extent of the central part of the country 
In the north of Ireland the Coal Measures differ from that of the 
south by the development of thick sandstones, forming a group like the 
Millstone grit of Derbyshire, and the separation of the Carboniferous 
Limestone by the introduction of a set of shales and sandstones called 
the Calp, with the entire absence of the Carboniferous slate group. 
The character of the Coal is also different, that of the north being 
Bituminous, whilst in the south it is Anthracitic.* 
In England the lowest division of the Carboniferous formation is 
known as Lower Limestone Shale; in Scotland, as the Lower Calci- 
ferous Sandstone; and in Ireland, Carboniferous Slate and Coomhola 
grit. 
Although the arenaceous and schistose Lower Carboniferous strata, 
“‘have” as Sir R. Murchison observes,} ‘¢a strong mineral and zoologi- 
eal affinity to the upper portion of the underlying Devonian, or Old 
Red Sandstone rocks, into which they graduate,” yet the fossils are 
sufficiently distinct to enable us to separate these formations, and more 
especially as we ascend in the series. 
The Plants of the Lower Carboniferous strata in Scotland are nu- 
merous in some districts, and resemble those of the true Coal Measures, 
such as the genera Sphenopteris Lepidodendron, Stigmaria, &c.t 
* Jukes, Manual of Geology, 1862, p. 515. 
¢ Siluria, fourth edition, p. 295. 
{ Prestwich, Geol. of Coalbrookdale, Geol. Trans., 2nd series, Vol. v., p. 463. 
