414 
EXCURSIONS. 
but this had to be relegated to an informal conversation after 
the meeting. 
The Chairman then called upon Dr. Wheelton Hind to give 
an address on the Carboniferous Rocks of North Wales. 
Dr. Hind first referred to the pioneer work done by Mr. 
G. H. Morton, pointing out that this had been carried out entirely 
on lithological lines, and that although in the main the results 
were in accord with those obtained by the more modern pala?- 
ontological methods, there was nevertheless considerable differ- 
ence as regards details, the palseontological breaks sometimes 
occurring in the middle of one of Morton's lithological zones. 
Ho then dealt with the nature of the floor underlying the 
Carboniferous Series, and was of opinion that there was a ridge 
of land separating North and South Wales, and that the northern 
part was not submerged until a much later period than the 
south. 
The zoning of the rocks was then treated of in considerable 
detail. 
In the discussion. Dr. Vaughan pointed out the ^;reat im- 
portance of the bathymetric level at which the different deposits 
were formed, and the necessity of giving full consideration to 
this in any attempt at zoning an alternating series of deep and 
shallovv^ water deposits. The shore fauna of any period being 
invariably different from the oceanic fauna, it follows that the 
assemblage of fossils will also vary as between deep and shallow 
water deposits. It therefore becomes necessary to set up two 
zonal scales — one for shallow, and the other for the deeper 
deposits. 
This does not necessarily affect the zoning of a mixed series 
of shales and limestones, as these may in reality belong to the 
same bathymetric level, the distribution of shales being con- 
trolled by varying currents. 
Mr. Cosmo Johns pointed out that the base of the Millstone 
Grit rests on beds o^ various ages in different parts of the country. 
With regard to the irregularity of the sub-Carboniferous floor, 
he stated that he had seen bedding lines in the lower part of the 
Carboniferous Limestone Series which passed up against hills 
on the underlying floor. 
