1 60 PARSONS I TRIAS OF THE VALE OF YORK. 
know, the line between the palaeozoic and secondary series of 
strata is drawn, on palseontological grounds, between the 
Permian and the Trias ; and in the south of England, where 
the Permian is wanting, the hiatus at the base of the Trias is 
as strongly marked as that between the chalk and the eocene. 
The varying degree to which, as shown on the maps of the 
Geological Survey, the upper magnesian limestone is over- 
lapped by the red sandstone, would seem to indicate that there 
is some amount of unconformability between them. In litho- 
logical characters, however, there seems to be a gradation 
between the two. At Hexthorpe, near Doncaster, the upper 
beds of the limestone are of a reddish colour, with partings of 
variegated red and green marl, and above them is a red 
sandy marl. In some places, as at Monk Fryston, there is a 
red marl with layers of gypsum closely resembling the 
Keuper marl, marked " e5 " in the Geological Survey map, 
which rests on the upper limestone. The only place where 
I have seen the red sandstone in contact with the limestone 
is in a quarry by the side of the railway at Monk Fryston, 
about half-a-mile south of Milford Junction. Here there is 
a fault recently exposed in cutting a new roadway into 
the quarry, and not shown in the Survey map, running nearly 
east and west, with the downthrow on the south, which has 
elevated the magnesian limestone into juxtaposition with a 
red and cream-coloured sandstone, which, though marked 
" e5 " Red Marl, in the Survey map, can hardly, I think, 
be anything but the Bunter sandstone. Altogether, the 
relations of the Trias and Permian form a difficult but 
interesting subject, well worthy of being worked out by an 
abler geologist than myself, in the way that our excellent 
Secretary has worked out those of the Permian and the Coal 
Measures. 
