The Ammonite Zones of the Upper Oxfordian of Oxford, and the Horizons of the Sowerbys' and Buckman's Types

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Abstract
It is more than a century since J. and J. de C. Sowerby figured in The Mineral Conchology , from the Corallian of the neighbourhood of Oxford, the type specimens of Ammonites plicatilis, Am. cordatus, Am. excavatus, Am. vertebralis and Am. catena , and since Brongniart made the district the type and standard of the Oxfordian stage, a term adopted by Marcou and, after emendation by d'Orbigny, eventually disseminated in the stratigraphical literature of the whole world. Nevertheless, in spite of the time that has elapsed and of the labours of S. S. Buckman in the district, the precise stratigraphical horizons and ranges of the Sowerbyan types remain obscure, as does also the whole succession of ammonite faunas. This obscurity is reflected in the variety of interpretations that have been put upon the term “Oxfordian stage” (see Arkell, 1927, pp. 154–5). I accept here the scope of the stage as stabilized by d'Orbigny (1852, p. 522: “l'Oxford Clay, le Calcareous Grit, le Coralline Oolite de M. Phillips” [the last the Oxford Oolite of Buckland and Fitton]) in which form (including, of course, the coral rags) it has also been accepted by Dr. Spath in his latest comprehensive table of Jurassic stages (1933, p. 872). The Upper Oxfordian as there represented, and as now commonly understood, corresponds with the Corallian beds in England and the Argovian and Rauracian substages on the Continent. In this paper I attempt to show the content of the Upper Oxfordian, with special referrence to ammonite horizons, in the

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