HUGHES : INGLEBOROUGH. 
53 
The Pale Slates are commonly interbedded with red and 
greenish grey shale. The conditions of sedimentation were now 
beginning to settle down, so that similar deposits were dis- 
tributed over large areas as compared with the banks of gravel, 
and pans and hollow places filled with black mud, which were 
characteristic of the basement beds. We still find thin beds 
of black shale here and there in the Pale Slates, and it is where 
these occur, that we most often meet with the traces of 
organisms ; but the Tarannon Shale of Wales and the Pale 
Slates of our district are generally barren. 
In the Pale Slates of Spengill I have found Monograptus 
Marri Perner, M. Hisingeri Carr., and (?) M. Becki Barr., but 
I have expressed a doubt when describing that section, p. 52, 
whether some of the beds which appear to be part of the Pale 
Slates may not rather be equivalent to portions of the Austwick 
Flags and Grits. 
The Austwick Flags. 
The Austwick Flags consist chiefly of sandy mudstone, with 
a tendency to split along the bedding into large flat masses, 
so that the name flags is appropriately applied to them in this 
district. The cleavage is not so strong as in the underlying 
Bala Series, but yet sometimes, when at a considerable angle 
to the bedding, it makes itself felt so far as to cause the rock 
to split across the bedding planes into large slabs. 
Among the fossils found in these beds were — 
Monograptus vomerinus Nich. 
M. priodon Bronn. 
M. personatus TuUbg. 
M. cultellus Tornq. 
Retiolites geinitzianus Barr. 
Orthoceras. 
Harkness and Nicholson noted that in the lower part of 
the Coniston Flags " a form possessing strong spines attached 
to the cell mouth is seen." This wp.s probably M. vomerinus. 
As time went on, sand was intermittently carried over 
this area, and indeed over the whole of the area between Ingle- 
borough and mid-Wales so far as the Northern type of Silurian, 
which I have described above (pp. 355-356), extends in that 
