I06 SILURIAN. 



At Malvern the Downton sandstones are about loo feet in thick- 

 ness ; there they consist of red, grey, and yellow sandstones and 

 marls. In the Woolhope district the Passage-beds have been 

 exposed at Perton, near Stoke Edith ;^ and here Pterygotus and 

 Eiirypterus were found in the olive (Ledbury) shales. (See Figs. 

 12, 13, 14 and 15.) 



The Downton beds are quarried near Downton Castle, and at 

 Dymock near Ledbury. They are represented by red sandstones 

 at Usk. 



The Passage-beds may be seen in the banks of Linley Brook, 

 near Broseley in Shropshire, where an upper Bone-bed occurs 

 above the Ludlow Bone-bed/^ At one time the junction of Upper 

 Ludlow and Lower Old Red Sandstone was well exposed near 

 Callaughton.^ 



Prof. Hull regards the Foreland group of Devonshire as con- 

 stituting the passage-beds between the Silurian and Devonian, 

 equivalent in fact to the Dingle Beds or Glengarift' Grits 

 of Ireland, to the Downton Sandstones, and to the purple and 

 reddish sandstones, shales, and conglomerates of the Ridge of 

 Trichrug, underlying the so-called " Old Red Sandstone " near 

 Llandovery. These passage-beds he speaks of as the Devono- 

 Silurian formation.* The Torquay and Fowey grits may also be 

 placed on the same horizon. (See sequel.) 



Ledbury Shales. 



This group, which was named by Mr. J. W. Salter from the town 

 of Ledbury, rests conformably upon the Downton Sandstones, and 

 merges gradually upwards into the Lower Old Red Sandstone. 

 Part of it might perhaps be grouped with that formation.* It 

 comprises red, grey, and purple marls, shales, and sandstones, 

 having at Malvern a thickness of 300 feet. 



The section exposed at the railway-tunnel near Ledbury was 

 described by Rev. W. S. Symonds as follows '.^ — 



Lower Old Red Red marls with grey and reddish sandstone, Pterygotus, Pteraspis, 

 Sandstone. and Ccphalaspis. 



Grey marl passing into red and grey marl and bluish-grey rock 

 (Auchenaspis-grits), with Auckenaspis, Ctphalaspis, Onckus, 

 Pterygotus, Lingula cornea, etc. 20 feet. 

 Ledbury Shales \ Purple shales and thin sandstones, Lingula. 34 feet. 



Grey shales and grit, with Cephalaspis and Pterygotus. 8 feet. 

 Red and mottled marls, and thin sandstones with Lingula, 



Pteraspis. 210 feet. 

 Downton sandstone. 9 feet. 



1 P. B. Brodie, Q. J. xxv. 236 ; xxvii. 256. 



2 G. E. Roberts and J. Randall, Q. J. xix. 229. 



3 Prestwich, T. G. S. (2), v. 422. 

 * G. Mag. 1878, p. 530. 



5 See J. E. Marr, Cambrian and Silurian Rocks, p. 47. 



^ Q. J. xvi. 193 ; xvii. 152 ; Records of the Rocks, p. 202. 



