HUGHES : INGLEBOROUGH. 
337 
peculiar to this horizon, they characterise it by the numbers of in- 
dividuals in proportion to other species, so that for convenience of 
local reference I formerly called these beds the Strophomena Shales. 
The same remarks apply also to the name Trinucleus Shale by which 
I referred to the overlying beds. Closer work will doubtless by-and- 
by divide the series into many palseontologically distinguishable 
zones. 
The whole series is nipped out by faults near Wood Lane and is 
not seen again to the E. 
The section is much complicated by a fault which may be seen 
crossing the stream a little above Dam House Bridge. The direction 
of this fault is slightly oblique to the strike of the Bala Beds, having 
a little more north and south in it, so that it brings the Silurian rocks 
against lower and lower beds of the Bala series as we follow it to the 
east-south-east. The beds of both series are similarly folded on the 
north or downthrow side of the fault, but, owing to the downthrow 
being on the north, higher beds of the Bala series are found in the 
tops of the anticlinal folds on the north side of the fault than are 
exposed in the corresponding and contiguous folds on the south of 
it. Thus in the stream close above the small waterfall which marks 
the exact position of and is due to the Dam House Bridge fault there 
is a small subordinate anticlinal which throws of! the basement bed 
of the Silurian on either side, so that black shales are exposed between 
two bands of conglomerate, the one with a northerly, the other 
with a southerly dip (see Figs. 12 and 13). It is probable that this 
is a pre-Carboniferous fault. 
In these black shales the following fossils have been found : — 
Orthis testudinaria Dalm. 
Strophomena siluriana Dav. 
They therefore represent the highest beds of the Bala seen in 
this district, and are the equivalent of the Strophomena siluriana 
beds so largely developed in the tributaries of the Rawthey, especially 
in Sarley Beck, some 15 miles X.N.W. of Wharfe. It was on speci- 
mens collected in Sarley Beck that Davidson founded the species 
siluriana. In the Lake District their equivalent is seen in the 
shales of Ashgill, near Coniston. 
