On the Western Limit of the Rhætic Beds in South Wales, and on the Position of the “Sutton Stone”

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Abstract
The object of the present paper is to notice some peculiarities of the Avicula-contorta series at their most westerly boundary in Great Britain; to discuss the. “Sutton Stone” as to its stratigraphical, lithological, and palæontological relations; to show from organic remains that its affinities are with the Triassic formation, and not with the Lias as commonly supposed, and then to claim it as Rhætic, and in so doing to extend, for the first time in England, the range of Ammonites down into the Rhætic series. At the Bath Meeting of the British Association for 1864, Sir R. I. Murchison announced the presence of the argillaceous limestones and shales of the Rhætic series in a small outlier of Lias (as mapped) close to Pyle Station (west of Bridgend); and having in this way had my attention directed to the subject, I found that the Avicula-contorta strata were widely extended in this district; and as they show some peculiarities here, I will begin by a few remarks on these beds. 2. Pyle district. —The above-mentioned patch, sufficiently described by Mr. Bristow*, consists of buff-coloured marls and greyish-brown shales and limestones, which last, from their appearance and conchoidal fracture, remind one of the Cotham marble: these are probably high in the series; they are mapped as lying on the Keuper. A few hundred yards south of this we reach the southern limit of the Keuper in this district. It consists of red marls with buff and green marls resting upon them; the same conditions

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