HIND : CARBONIFEROUS ROCKS OF THE PENNINE SYSTEM. 445 
This is important, but unfortunately the Four Laws or Wood- 
end Limestone at the Coomb, south of Redesdale, has yielded to Mr. 
Dunn and myself a fauna which contains all the special fossils {lamelli- 
branchs and gasteropoda) which have been found at Lowick. Now, 
Mr. Gunn places the Four Laws Limestone much lower than the 
Acre. Who shall then decide whether the Cat Craig Limestones 
are the equivalents of the Acre or the Four Laws Limestone, more 
especially when it is known that the beds are undergoing rapid changes 
as they pass north ? 
It seems to me more than possible that the initial mistake in the 
nomenclature of the Yoredale Limestones has been to reckon them 
from below upwards. The Millstone Grit at the top might have 
been taken as a base line with a good deal more reason than the 
continually altering top of the Great Scar Limestone as it becomes 
split up by intercalations of shale to the north. 
Perhaps a full and accurate paleontological survey would give 
some more certain ground for correlation, though I am bound to 
say at present I have obtained no direct evidence to enable one to 
approach the subject -with any degree of accuracy. As the beds 
pass north, owing to the muddy sediment and the probable shal- 
lomng of the sea, new forms of life occur plentifully, which were 
not met with in the massive limestones, but similar faunas occur 
again and again at different horizons. 
Professor Lebour has given some excellent lists of fossils from 
certain of the Northumberland limestones in his Handbook to the 
Geology and Natural History of Northumberland, from which it 
will be seen how very similar were the faunas obtained at different 
horizons. I append lists of fossils which I have obtained in the Redes- 
dale district from the Redesdale and Four Laws Limestone series. 
Professor Lebour shows that Produdus gigantens is found in 
the Fell Top Limestone of Northumberland, but at present I have 
no evidence that this fossil occurs above the Main Limestone in Wear- 
dale or Wensleydale. 
Last August my attention was called to a book on " The Laws 
which regulate the Deposition of Lead Ores," by W. Wallace, published 
in 1861. In it is a plate (Plate lY.) which gives hi? idea of the corre- 
lation of the Carboniferous deposits of England- 
