HUGHES : mOLEBOROUGH. 
67 
over Bala Beds, and we might expect to find the base of the 
Silurian if we could remove the superficial deposits. 
The Horton Flags are seen in these three sections to lie in 
a synclinal trough, the axis of which slopes gently to the east, 
so that we see only a little of the flags in Crummack Dale, 
more along the west flank of Ribblesdale, and the whole, up to 
the base of the overlying Studfold Sandstone, along the east 
flank. 
The Horton Flags are the equivalent of the Upper Coniston 
Flags of the Lake District and of the Nantglyn Flags of North 
Wales. 
As happens in so many cases, the fact of their being of 
commercial value helps to give them a geological importance, 
because they are rendered accessible in quarries, fresh surfaces 
are exposed for investigation, and the workmen preserve fossils 
for the collector. In this case it would have been especially 
difficult to procure fossils on the weathered outcrops. They are 
not often abundant even when we have thousands of feet of 
freshly split flags in which to search for them. 
In the great quarry at Arco Wood I found Trochoceras gigan- 
teum Sow. in situ ; Actinocrinus pulcher Salt., etc., but the best 
locality for fossils is in the quarries along Dry Rigg a little 
further south, where they very commonly occur in calcareous 
concretions, and from which all the following fossils, except the 
Trochoceras, have been procured : — 
Orthoceras primoevum Forbes. 
0. Sedgwicki Forbes (? = 0. tenuicinctum Portl.). 
0. sp. 
Meristella tumida Dalm.? 
Cardiola interrupta Brod. 
Pterincea tenuistriata McCoy. 
Actinocrinus pulcher Salt. 
Favosites fibrosus Goldf. 
F. sp. small form akin to F, gothlandica, 
Trochoceras giganteum Sow. 
Monograptus colonus Barr. 
M. hohemicus Barr. 
M. rtEmeri Barr.? 
