136 PROCEEDINGS COTTESWOLD CLUB 1916 
is a soft sandy shale corresponding to the Wenlock Shale beds 
on the Eastern side of the river. It is not until one gets to a 
spot opposite Kemeys Commander that any reliable dip can be 
obtained, and here it is 25° N.E. The rock is a sandy shale 
containing a few layers of calcareous nodules, and it overlies 
irregular layers of limestone with sandy shales between them. 
More sandy shales are seen at a spot about half a mile further 
down the river, where the dip is 48° S.W. The exposures in 
the river bank near Trostrey are also in sandy shales, which 
contain layers of calcareous nodules and thin limestone bands 
and dip at low angles to the South. 
Similar beds are seen round Trostrey and Little Trostrey, 
and to the East of Trostrey Court. Amongst them occur 
layers of sandstone, which, just above Little Trostrey, contain 
Homalonotus Johannis, which, according to Salter, is a typical 
Usk species in the Wenlock Shales'; while to the North-East 
of this exposure occur irregular limestone-layers resembling 
those mentioned as having been found on the West bank of 
the Usk opposite to Kemeys Commander. 
Further to the North, a quarry close to the road leading 
from Bettws-Newydd to the Chain bridge proves that these 
sandy beds extend as far as that point. 
Their lithological resemblance to the upper beds of the 
Wenlock Shale of the southern part of the area makes it prob- 
able that they too are high up in the Wenlock Shale beds. 
But although this is no doubt the case, there is no regular dip 
to the North amongst them, and the domical arrangement of 
the Usk Silurian beds so often referred to in accounts of the 
area is not borne out by dip observations. 
Between Trostrey and Rhadyr the Usk runs up against 
the ridge of Craig-y-Garcyd, and has cut a line cliff face in 
dark grey mudstones, which he horizontally. These often 
show a concretionary structure, and are very fossiliferous. 
All these exposures of Wenlock Shales serve to show that 
in the L^sk Area these beds may be divided up into 
1. Upper SiiALKs ; brown sandy shales with sandstone bands near their 
summit and occasional calcareous bands and nodules in 
their lower parts. 
2. Lower Shales ; grey mudstones. 
1 J. W. Salter, British Trilobites, Palieont. Sue. (1864-1883), pp. 117-119. 
