CAMBRIAN ROCKS IN SOUTH SHROPSHIRE. 657 



first suggested that the sandstone of Acton Pigott might be Carbo- 

 niferous. But the discovery in it of Orihis vespertilio and Favosites 

 Jibrosus clearly established its Cambro-Silurian age; and further 

 evidence convinced me that it, as well as the sandstones near 

 Harnage, represented the Hoar-Edge Grits. 



This branch of my subject I leave for the present, the chief 

 purpose of my paper being the description of the older rocks of the 

 neighbourhood. 



The Shineton Shales. 



The locality where I first observed these shales is the spot near 

 Shineton marked on the Geological-Survey Map with an arrow 

 dipping to the south-east at 50°. The rocks are there exposed in 

 two good sections on the left bank of the stream. It is from these 

 sections that most of the characteristic fossils have been obtained ; 

 and I have therefore named the formation from this locality. 



1. Area. — These shales cover an area extending from near Even- 

 wood, on the south-west, to within a mile of Wellington, on the 

 north-east, a distance of eight miles. Their greatest breadth, from 

 Shineton to Dryton, is about two miles ; but where they range 

 towards Wellington it is contracted almost to a point. The area is 

 roughly triangular in shape, the apex of the triangle pointing to the 

 north-east. Its north-west side is bounded by a fault or faults for 

 probably its entire length, various formations from the Hollybush 

 Sandstone to the Trias abutting against the shales. On the south- 

 east side, the triangle is covered in by intrusive basaltic rocks for 

 one third of its distance from the apex, and the remainder by the 

 May-Hill Sandstone. The base of the triangular area is limited by 

 the Hoar-Edge Grits. It is not improbable that the Shales will also 

 be found under the Hoar-Edge Grits to the south-west*. 



2. Lithological Characters. — The Shineton Shales are dark blue, 

 weathering to olive and yellow, the colouring iron-oxide sometimes 

 separating as a stain or film. They are micaceous, thin-bedded, 

 soft, and rather fissile. On the Severn, near Cressage, and at 

 Leighton Mill, my friend the Eev. C. Croft, of Newtown, has 

 detected calcareous nodules ; and we have collected similar specimens 

 near the base of the series in a stream below the road | mile 

 east of Bank's Lane. At the top of the series, where it passes 

 under Caradoc rocks, the shales become more arenaceous and 

 thicker-bedded, and present the characters of a shore-deposit. 



3. Relations to surrounding Formations. — Commencing at the 

 apex of our triangular area on the south-east side, the shales are 

 overlain for a distance of nearly two miles by basaltic rocks intruded 

 into the Carboniferous series. Eor the next five miles to the south- 

 west they are succeeded unconformably by the May-Hill Sandstone. 

 At the base of our triangle they dip with apparent conformity under 

 the Hoar-Edge Grits. The north-west side is probably entirely 

 limited by faults, the formations being brought against the shales 



* There is little doubt that the valley between the Lawley hill and Hoar Edge 

 is hollowed out of Shineton Shale. 



