74 Professor Epwarp Hurr—On the Nature and Origin of Beds of Chert. 
being mapped out in detail. Beginning in the north-western districts we find the 
following series :-— 
FERMANAGH, SLIGO, &c.—SECTIONS OF THE CARBONIFEROUS LIMESTONE, 
Shales with Goniatites, &c. 
seaneeiale Bods : Yellow Sandstone. 
Upper Limestone with Chert. 
Carboniferous Limestone (2,500 feet) < Middle or Calp Series. 
Lower Limestone. 
Lower Carboniferous Sandstone, &c. 
The lower limestone occurs at Enniskillen, and along the banks of Lough Erne ; 
it consists of bluish massive shelly and crinoidal limestone, with occasional bands 
of shale. 
The middle or calp limestone consists of a thick series of dark earthy limestones 
and shales, the dark matter is carbonaceous, and is probably due to marine alge ; 
small bivalve shells are numerous, and likewise the trumpet-shaped coral, Zaphrentis 
cylindrica. 
The upper limestone consists of massive coralline and crinoidal limestone, with 
beds of chert, which occur in greatest mass at the top, immediately below the 
Yoredale sandstone. Corals and crinoids are sometimes preserved in this chert. 
The upper limestone forms a range of hills, with scarped faces along the western 
shores of Lough Erne, also numerous isolated or prominent hills with scars or 
terraced sides, such as Benbulbin and Knock-na-Rea near Sligo, and Keshcorrau 
on the borders of Leitrim. It is the most prominent member of the whole series in 
this part of Ireland, its great mural cliffs rising conspicuously above the slopes 
and valleys of the subordinate beds of the middle series, which being largely 
composed of soft shales and earthy limestones, seldom rise into the hilly ground, or 
give rise to marked features. 
In the eastern districts of Ireland, the three divisions of the limestone are 
sufficiently characteristic, especially, on all sides of the Leinster and Tipperary coal 
basins—the following general section by Mr. J. O'Kelly of the Geological Survey 
of the beds, as they occur in the Queen’s County, may be considered typical of 
the district.* 
SECTION OF THE CARBONIFEROUS LIMESTONE OF THE QUEEN’S CounryY. 
Shale Series (Yoredale Beds). Black and dark gray shales. 
Upper Limestone. Thick, regularly bedded, pale bluish crystalline limestone, in which 
layers and nodules of black and white chert are very common, par- 
ticularly in the upper beds, the lower beds are magnesian to the west 
of A bbeyleix. 
Calp or Middle Limestone. Black and dark gray, impure flaggy limestones and shales. 
* “Explanation” to sheet 127, of the. maps of the Geological Survey. The section is somewhat 
abbreviated. 
