152 HIND : CARBONIFEROUS ROCKS OF ISLE OF MAN. 
In Swinden Gill the beds with Z. Enniskilleni overlie mas- 
sive limestones in which a caninoid Campophyllum is very- 
common. 
Both in Yorkshire, as at the Craven knolls, and in North 
Wales, at Axton and near Meliden, highly fossiUferous, knoll- 
like beds of white limestone occur, containing a similar fauna 
to the Poolvash shell beds. Their relation to the Zaphrentis 
Enniskilleni beds or well-bedded coralline limestones is obscure, 
and they seem to in some way replace them ; but wherever 
Zaphrentis Enniskilleni comes on, the Posidonomya Becheri beds 
may be expected to succeed them in each case. 
This fossil appears to characterise all the well-bedded 
limestones of the Isle of Man, but it is absent in the white lime- 
stones of Poolvash, Nor does it appear to have a very wide 
vertical range. 
In the Yorkshire area it first appears in black shales over- 
lying the Hardraw Scar Limestone, with a typical Upper 
Dibunophyllum fauna. I believe it has never yet been found in 
the Bristol area, but I have found it, or a very close relative, in 
the black limestone of Oystermouth Castle, in the Gower penin- 
sula, associated with trilobites and other members of the Upper 
Dibunophyllum zone. 
Hence I rely locally on this fossil to give a definite index 
for the correlation of the various outliers or isolated exposures 
of the well-bedded limestones of the south of the Isle of Man. 
The Derbyhaven beds have given me much food for thought. 
The fauna there contains corals which are generally considered 
to have a low facies, for example, Michelinia megastoma, and 
the view is somewhat strengthened by the presence of a large 
Chonetes, of a Chonetes comoides character, but with a much 
thicker shell than the C. comoides of the Bristol-Mendip area. 
But Zaphrentis Enniskilleni, on the other hand, always denotes a 
high horizon in the Dibunophyllum zone, and this is very abundant 
in the Derbyhaven-Ronaldsway sequence. There can be no 
doubt of the Dibunophyllum age of the sequence at Scarlet, which 
contains Cyclophyllum, Cyathaxonia, and Z. Enniskilleni as well 
as the Campophyllid corals. At Derbyhaven some of these corals 
