58 
huc;hes : ingleboroxjgh. 
by Professor Judd* in the case of the Northamptonshire iron- 
stone. A number of graptolites have from time to time been 
obtained from these beds. Miss EUes has referred them to the 
following species : — 
Monograptus duhius Suess. 
M. nilssoni Barr. 
M. uncinatus Tullb., 
and considers that they indica.te a somewhat higher horizon 
than that of the Austwick Flags and Grits, in the lower part 
of which they seem to occur, on the supposition that the faults 
shown in section, Fig. 6, have no great downthrow. If they 
should, on palaeontological grounds,! be referred to the base of 
the Horton Flags, there must be a fault shifting the beds in 
the manner suggested in the diagrammatic ground plan. Fig. 4, 
p. 57. 
The occurrence of Orthoceras primcevum Forbes, which has 
been found in the same beds, is not inconsistent with this view. 
The Horton Flags. 
This series consists of a sandy mudstone, splitting into 
flags of enormous size (see Fig. 5). There is a rough cleavage, 
but when this approaches within 15° or so of the bedding planes, 
the rock splits along the beds and the cleavage is practically 
obliterated. When the cleavage predominates, the rock splits 
along it into rough slabs, which are found useful for building 
or walling. There are subordinate more sandy beds of irregular 
occurrence, but as rocks yielding the large flags are what are 
most sought in choosing a place to open a quarry, those 
parts were avoided in which such sandstones or grits occurred, 
or where the direction of the cleavage did not lend itself to 
the production of good flags. 
In the examination of any area of cleaved rocks, it will 
be found that the normal cleavage is very persistent in direction 
and inclination — more so in direction than in inclination — and 
its direction generally coincides with the strike of the rocks. 
* Mem. Geol. Siirvey, Geology of Rutland, 1875, pp. 135-6. 
t of. Marr, Geol. Mag., dec. iii., vol. ix., 1892, p. 534. 
