LIFE-ZONES IN THE BRITISH CARBONIFEROUS ROCKS. 227 
Treland gradually dies away south-west of Cork, and in the succession at 
Old Head of Kinsale, and from that point westward no Limestone 
whatever occurs, but instead there is a thick mass of Grits and Slates, 
which have been called Lower Limestone Slates and Coomhola Grits. 
It is also known that the passage up from the Devonian Grits to 
Coomhola Grits is unbroken, and that the one series has no top and the 
other has no base. The Coomhola Grits are, however, fossiliferous and 
contain shells referred to Ptychopteria Damnonensis, Cucullea uni- 
lateralis, species which occur in the Pilton and Marwood series of Devon- 
shire. These beds are always classed as Upper Devonian in England, and 
therefore it would be well for the same line to be drawn in Ireland. The 
whole fauna from the Coomhola Grits should be re-examined, because I 
think it probable that trilobites and other species have been referred to 
Carboniferous forms on the supposition that the Coomhola beds were 
Carboniferous. The Coomhola Grits are overlaid by the Lower Carboni- 
ferous Slate, part of which is indeed of Carboniferous age, because it 
contains Posidonomya Becheri. Here then is a point of great interest. 
Beds with a Marwood and Pilton fauna are overlaid by grey shales and 
then by black with P. Becher; and in North Devon the Pilton beds are 
succeeded by the Lower Culm with P. Becheri in abundance in the Venn 
Limestones. In both districts the Devonian Carboniferous succession, 
apparently unbroken and conformable, is from Marwood and Pilton beds 
to Pendleside Series, the Carboniferous Limestone being absent in each 
locality ; and if there is no unconformity it follows that the Carboni- 
ferous Limestone was never laid down in the North Devon, Cork, and 
Kerry latitude. 
Jukes considered that the Carboniferous Slate of South-west Ireland 
was contemporaneous with the Carboniferous Limestone, and his views 
are given at length, pp. 33-37 of the ‘ Memoir of the Geological Survey’ 
(Ireland), Explanations of Sheets 187, 195, 196 of the maps. He 
visited North Devon and says: ‘TI saw that both lithologically and 
palzontologically, bed for bed, and fossil for fossil, the Braunton and 
Piltown rocks of Devon were identical with the Carboniferous slate of 
Cork. The Marwood sandstones and the grey grits below them that 
form.Baggypoint were obviously the same as our Coomhola Grits, and the 
red and green rocks that rise up from beneath those rocks in Morte Bay 
are exactly similar to the Upper Old Red Sandstone of large parts of the 
west of County Cork. 
‘But the Coal Measures’ (by which I suppose he means the Culm, and 
I would that all subsequent geologists had recognised the Coal Measure 
horizon of these beds) ‘of Devon rest on the Carboniferous slate without 
intervention of any Carboniferous Limestone in its ordinary form, often 
without any appearance of limestone at all.’ But he carries his argu- 
ment too far, for he goes on to say: ‘If, however, we have Coal Measures 
above and Old Red Sandstone below, the rocks between them must be of 
the age of the Carboniferous Limestone.’ 
The Lower Culm is, I am convinced, of later age than the Carboniferous 
Limestone, and is the homotaxial equivalent of the Pendleside series, 
How comes it, therefore, that the Coomhola Grits and the grey portion of 
the so-called Lower Carboniferous Slate are mapped as Carboniferous 
instead of Upper Devonian ? 
The view advanced by Jukes, that the Carboniferous Slate is con- 
‘emporaneous with the Carboniferous Limestone, is probably correct, the 
Q2 
