142 OLD RED SANDSTONE. 



UPPER OLD RED SANDSTONE. 



The Upper Old Red Sandstone consists of red, variegated, 

 and yellowish-grey sandstones, quartzose conglomerates, and red 

 marls, attaining a thickness estimated at 4000 feet. 



In the West of England and in South Wales the conglomerates 

 occur chiefly at the base ; they are overlaid by red marly beds, and 

 these are succeeded by red and yellowish-grey sandstones, which 

 pass upwards, as in Dean Forest and on the Mendip Hills, into 

 the Lower Limestone Shales. 



The organic remains comprise some plant-remains, such as 

 Sphenopteris, Sagcnaria or Lepidodcndron {Kiiorria), etc., including 

 the earliest known British fern, and the earliest traces of Equise- 

 tacese and Gymnosperms (Conifers). The more conspicuous fossils 

 are the iishes Holoptychius and Pterichthys. The Pteropod Conularia 

 has also been met with. 



The most westerly beds of Old Red Sandstone occur in 

 Pembrokeshire, where they comprise alternations of conglomerate, 

 with sandstone and marl.^ Specimens of Serpula were found by 

 Mr. Salter in the upper beds of Caldy Island.- Slaty cleavage in 

 nearly vertical lines traverses the beds around Milford Haven. 



The Brecknockshire Beacons, which rise to a height of 2862 

 feet, and the Vans of Brecon and Caermarthen, forming a range 

 sometimes called the Black Mountains,' are composed of Old Red 

 Sandstone. The rocks on the summit of the Brecknockshire 

 Beacons consist of the Brownstone series, which is overlaid by 

 beds of conglomerate. There is a white marly quartzose con- 

 glomerate on the Brecknockshire Vans similar to that on the 

 Scyrrid, and to beds which cap the Caermarthenshire Beacons : 

 this is the basement bed of the quartzose conglomerates.* 



Conglomerate is exposed on the Blorenge above Abergavenny, 

 in the banks of the Wye from Ross to Monmouth, and west of 

 INIitcheldean. Quartz-conglomerates occur on the hills near 

 Monmouth, where enormous blocks of this rock and small isolated 

 tors occur, as on Kymin Hill and the "Brick-stone" not far off.® 



The Brownstone Series, described by the Rev. W. S. Symonds, 

 consists of red marls and shales, chocolate-coloured sandstones 

 and flagstones, and thin cornstones. It contains fragments of 

 Ccphalaspis and Phraspis. The beds are quarried above Bitterly 

 Court, west of Titterstone Clee, and at Abdon and Ditton below 

 the Brown Clee ; and the beds may be seen near Tenbury.^ (See 

 pp. 118, 119.) The precise relations of these beds have yet to be 

 determined. 



' De la Beche, Mem. Geol. Surv. i. 62, no. 



' Q. J. xviii. 476. 



^ These are distinct from the Black Mountain between Abergavenny and Hay. 



^ Records of the Rocks, p. 246. 



^ Buckland and Conybeare, T.G.S. (2), i. 2S0. 



8 Records of the Rocks, pp. 212, 241. 



