HUGHES : INGLEBOROUGH. 
357 
while to make a careful search along the horizon where the 
Ashgill Sliale might be expected across the Crummack valley 
to the east. Near the waterfall by Wharfe Mill Dam, how- 
ever, it does seem to be represented by certain black shales 
cropping out below the conglomerate which here occurs at the 
base of the Silurian. 
A troublesome fossil which occurs in the Ashgill Shale here, 
but is far more common and well preserved at the same horizon 
east of Sedbergh, is Stroyhomena siluriana. It is not yet quite 
clear whether this fossil is confined to the Ashgill Shales, or 
whether it passes up into the basement bed of the Silurian, 
but I will postpone the consideration of this point till I come 
to the Silurian. 
General Sketch of the Geographical Distribution of the 
Silurian Rocks under Ingleborough. 
The Silurian rocks of the Ingleborough district roll over in 
spoon-shaped anticlinals and synclinals, and are exposed in the 
Crummack valley, in Ribblesdale,* and still further east out 
of our district. Several of the folds can be identified from one 
valley to another, so that we can conjecture with great certainty 
what the character of the surface would be like if we could take 
away the great tabular masses of Mountain Limestone, such as 
that of Moughton which covers the Silurian between Ribblesdale 
and the Crummack valley. 
The character of the folds, neglecting minor faults and 
puckerings, is shown in the ground plan diagram. Fig. 2.t The 
newest beds, or those marked Ab4, are the tough gritty sand- 
stones seen on the east side of Ribblesdale in Long Lane, south 
of Studfold, especially near the guide post. This division does 
not appear again in the Ingleborough area, but there are higher 
beds of this stage exposed in the wild country known by the 
appropriate name of Rough Lands, north-east of Great Stain- 
forth. 
♦Plate XL., Figs. 1 and 2, Proc. Yorks. Geol. and Polytec. Soc, 
Vol. XV., Part II. 
t This Diagram is reproduced here from Proc. Yorks. Geol. and Polytec. 
Soc, Vol. xiv., p. 332. 
