194 
HUGHES : INGLEBOROUGH. 
appears to be an outlying patch of the base of the Mountain 
Limestone is seen resting with a small east-south-easterly dip 
on the very irregular jagged edges of Silurian rocks dipping 
50°, S. 25° W. The surface of the older rocks does sometimes 
appear to have been weathered, as we see similar rocks weathered 
in a river bed. and this is what might have been expected from 
our finding parts of the surface scooj^ed out into small troughs, or 
even cut down into deep valleys, while on the wide, gently 
undulating plateaux we find the surface planed off and all jagged 
edges removed. 
I would now call special attention to some interesting 
points which want working out. First, there is, even within this 
small district, a different character in the basement deposits of 
different areas. For instance, in the northern part of Chapel-le- 
dale there is, as I have shown, a black limestone seen associated 
with it on both sides of the valley. Now black limestones ha\e 
a meaning. They are like danger signals telling us to look 
out for some change. Here is one as the Carboniferous sea is 
encroaching. There is another which, to enable people to find 
it. we may call the Hunt Pot Limestone. It occurs at the top 
of the Mountain Limestone just before it is giving way to the 
change of conditions which ushered in the Yoredale rocks. 
There is another on top of Simon's Fell, just above the last 
good limestone of the Yoredale rocks, when the vast sediments 
of the Millstone Grit and Coal Measures are coming on, in which 
there is hardly a trace ot limestone, save some poor little beds 
known as Crow Limestone in the Millstone Grit Series. 
The two upper black limestones which I have mentioned are 
very interesting palseontologically. In the Hunt Pot Lime- 
stone the Prodiicta gigantea is abundant, with a well-marked 
elongated variety, ? P. latissimus, which is said to mark higher 
horizons further north.* It is seen no more till we get up to 
the top of the Upper Scar Limestone on Simon's Fell, where 
another development of P. gigantea is found, with an elongated 
variety, P. Eddhurgensis, considered to be specifically different 
from that found at Hunt Pot. 
* See Garwood and ]Marr, Geol. Mag., 1895, p. 551. 
