196 PROCEEDINGS OF THE GEOLOGICAL SOCIETY. [Nov. 2, 



escarpments beautiful to look upon, and reduce to the uniformity of a 

 railroad-cutting an exhibition of a peculiar series of rocks which the 

 geologist has long hoped to behold in situ. He may never have the 

 opportunity again ! 



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

 (Auchenaspis-beds) (No. 12). 



I consider these beds as the equivalents of those liver- coloured 

 and greyish rocks, with the remains of crustaceans and fish, described 

 by Mr. Lightbody in the railroad- cutting at the railway-bridge, near 

 Ludlow. The mineral character of the Ledbury deposits differs con- 

 siderably from those of Ludlow, hard stone being much more de- 

 veloped at Ledbury, whereas at Ludlow shale is the character of the 

 deposit. The Ludlow beds, however, contain "pockets" of stone, 

 enveloped in shale, which I could not distinguish from the thick- 

 bedded building-stone of Ledbury, that contains such an abundance 

 of the Auchenaspis Salteri, Egerton, a figure of which is given in the 

 Quarterly Journal of the Society, vol. xiii. pi. 9. fig. 4, and by Sir 

 Eoderick Murchison in 'Siluria,' new edit. p. 155. In the Ledbury 

 beds, Henry Brooks has also detected portions of the fossil fishes 

 Pleetrodus, Cephalaspis, Pteraspis, and Onchus. Pterygotus Ludensis 

 also occurs, with a large Lingula. The Auchenaspis is so abundant, 

 that as many as four heads have been found upon a small slab a foot 

 in diameter ; the tail and body of this fish are as yet unknown. The 

 Auchenaspis-beds at Ledbury are 15 feet thick, and pass upwards 

 conformably into a series of red marls, with yellowish-grey and pink 

 sandstone, containing the relics of Pteraspis and Cephalaspis, which 

 are undoubtedly the base of the Cornstone series of the Old Red 

 Sandstone. Sir R. I. Murchison ranks the Cornstone -beds of the 

 Old Red Sandstone as the base of the series ; and undoubtedly, in 

 some instances, thin Cornstones are mineralogically developed near 

 the bottom of the Old Red ; but the Cornstones of Herefordshire, as 

 described by Sir Roderick in the 'Silurian System', the Cornstones 

 of Wall Hills, near Ledbury, of Foxley, Whitfield, Ewyas Harold, 

 Orcop, and Abergavenny are, I am convinced, at least two 

 thousand feet above the Downton sandstone, or highest Silurian 

 deposits. 



The thick subcrystalline cornstones just alluded to are also, I 

 believe, higher in the Old Red series than the thin bands, inter- 

 stratified with sandstone, which are quarried near Leominster, at 

 Leyster's Pole, and many other places, and the characteristic fossils 

 of which are Cephalaspis Lyellii, Pteraspis Lloydii, and Pter. 

 Lewisii. Mineralogical nomenclature, therefore, is inappropriate 

 when applied to the physical position of rocks, and apt to mislead 

 those not conversant with the mineralogical peculiarities of different 

 districts. 



The word "tilestones" (now happily abandoned by Sir R. Murchi- 

 son) is altogether inappropriate as applied to the Ledbury rocks. 



There is not a stone capable of being formed into a tile, from the 

 Downton sandstone to the cornstones of Wall Hills; but there are 



